Amish-Style Baked Cheese and Onion Tart

Sweet, slowly caramelized onions and sharp cheddar make this Amish-inspired tart wonderfully comforting. A flaky butter crust holds a tender, savory custard seasoned with a little Dijon mustard and thyme. Serve it warm for brunch, lunch, or a light supper with a crisp green salad.

Quick Recipe Version (TL;DR)

• Yield: 8 servings; one 9-inch deep tart
• Prep Time: 25 minutes
• Cook Time: 1 hour 40 minutes
• Total Time: 2 hours 30 minutes, including chilling and cooling, with some tasks overlapping

Quick Ingredients

• Pastry: 1 1/4 cups (156 g) all-purpose flour, 1/4 teaspoon fine salt, 8 tablespoons (113 g) cold unsalted butter, and 3–4 tablespoons (45–60 ml) ice water
• Onions: 1 1/2 pounds (680 g) yellow onions, thinly sliced; 2 tablespoons (28 g) unsalted butter; and 1 tablespoon (15 ml) olive oil
• Custard: 3 large eggs, 3/4 cup (180 ml) whole milk, and 1/4 cup (60 ml) heavy cream
• Cheese: 6 ounces (170 g) sharp cheddar, freshly grated, about 1 1/2 cups
• Seasonings: 1 teaspoon Dijon mustard, 1 teaspoon fresh thyme leaves or 1/4 teaspoon dried thyme, 1/2 teaspoon fine salt divided, and 1/4 teaspoon ground black pepper

Do This

• 1. Cut the cold pastry butter into the flour and 1/4 teaspoon salt. Add ice water just until the dough holds together. Form a disk and refrigerate for 30 minutes.
• 2. Meanwhile, cook the onions in 2 tablespoons butter and the olive oil with 1/4 teaspoon salt over medium-low heat for 40 minutes, stirring regularly, until deeply golden. Stir in the thyme and let cool slightly.
• 3. Roll the dough into a 12-inch circle and fit it into a 9-inch tart pan at least 1 1/4 inches deep. Refrigerate for 15 minutes. Heat the oven to 400°F (200°C).
• 4. Line the pastry with parchment and fill with pie weights. Bake for 20 minutes, remove the weights and parchment, then bake for 5 minutes more. Reduce the oven to 375°F (190°C).
• 5. Whisk the eggs, milk, cream, mustard, remaining 1/4 teaspoon salt, and pepper until smooth.
• 6. Spread the onions and 1 cup of cheddar in the shell. Pour in the custard and scatter the remaining 1/2 cup cheddar over the top. Bake for 35 minutes, until golden and the center reaches 160°F (71°C).
• 7. Let stand for 20 minutes before slicing. Serve warm with a crisp green salad.

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Why You’ll Love This Recipe

• Big flavor from everyday ingredients: Slow-cooked onions bring natural sweetness that balances the sharp cheddar.
• A beautifully flaky crust: Cold butter and a quick blind bake help keep the pastry crisp beneath the filling.
• Rich without being heavy: A combination of milk and cream creates a tender, sliceable custard.
• Easy to plan ahead: Prepare the pastry and onions in advance, or bake the whole tart a day before serving.

Grocery List

• Produce: 1 1/2 pounds yellow onions, about 3 large; fresh thyme
• Dairy: Unsalted butter, sharp cheddar, whole milk, heavy cream, and 3 large eggs
• Pantry: All-purpose flour, olive oil, Dijon mustard, fine salt, and ground black pepper; dried thyme if replacing fresh

Full Ingredients

Equipment: A 9-inch metal tart pan with a removable bottom, at least 1 1/4 inches deep; a rimmed baking sheet; a large skillet, preferably 12 inches wide; parchment paper; and pie weights or dried beans. A 9-inch deep-dish pie plate also works, although the baking time may be slightly longer.

For the Flaky Pastry

• 1 1/4 cups (156 g) all-purpose flour, plus a little extra for rolling
• 1/4 teaspoon fine salt
• 8 tablespoons (113 g) cold unsalted butter, cut into 1/2-inch cubes
• 3 tablespoons (45 ml) ice water, plus up to 1 tablespoon (15 ml) more as needed

For the Caramelized Onions

• 2 tablespoons (28 g) unsalted butter
• 1 tablespoon (15 ml) olive oil
• 1 1/2 pounds (680 g) yellow onions, weighed before peeling, halved and sliced about 1/8 inch thick
• 1/4 teaspoon fine salt
• 1 teaspoon fresh thyme leaves, or 1/4 teaspoon dried thyme
• 1 tablespoon (15 ml) water as needed to loosen browned bits during cooking

For the Cheese Custard

• 3 large eggs
• 3/4 cup (180 ml) whole milk
• 1/4 cup (60 ml) heavy cream
• 1 teaspoon Dijon mustard
• 1/4 teaspoon fine salt
• 1/4 teaspoon ground black pepper
• 6 ounces (170 g) sharp cheddar, freshly grated, about 1 1/2 cups, divided

Step-by-Step Instructions

Step 1: Make and chill the pastry

Whisk the flour and 1/4 teaspoon salt in a large bowl. Add the cold butter cubes and work them into the flour with a pastry blender or your fingertips until the mixture looks crumbly, with some pea-sized pieces of butter remaining. Those little pieces help create flaky layers.

Drizzle in 3 tablespoons of ice water and toss gently with a fork. Squeeze a small handful: if it holds together, the dough is ready. If it falls apart, add the remaining water 1 teaspoon at a time, using only what you need. Press the dough into a disk about 1 inch thick, wrap, and refrigerate for 30 minutes.

Step 2: Slowly caramelize the onions

While the dough chills, melt 2 tablespoons butter with the olive oil in a large skillet over medium heat. Add the sliced onions and 1/4 teaspoon salt, then reduce the heat to medium-low. Cook uncovered for 40 minutes, stirring every few minutes and more often toward the end.

The onions should become soft, reduced in volume, and a rich golden brown. If they begin sticking or developing dark patches, lower the heat and stir in 1 tablespoon water to loosen the browned bits. Let that moisture evaporate before continuing. Stir in the thyme during the final minute, then remove the skillet from the heat and let the onions cool until warm rather than hot. If the onions are still pale after 40 minutes, give them another 5–10 minutes; their color matters more than the clock.

Step 3: Line the tart pan

On a lightly floured surface, roll the chilled dough into a 12-inch circle about 1/8 inch thick. Carefully transfer it to the tart pan, easing it into the corners without stretching. Press gently against the sides, trim the excess level with the rim, and use any scraps to patch thin spots.

Refrigerate the lined pan for 15 minutes. Meanwhile, position an oven rack in the lower third of the oven and heat the oven to 400°F (200°C). Set the tart pan on a rimmed baking sheet so it is easier to move without pressing on the removable base.

Step 4: Blind-bake the pastry shell

Line the chilled pastry with parchment paper, leaving enough overhang to lift it out easily. Fill with pie weights or dried beans, making sure they support the sides as well as cover the bottom.

Bake for 20 minutes. Carefully lift out the parchment and weights, then bake the empty shell for 5 minutes more, until the bottom looks dry and the edges are just beginning to turn golden. If the base puffs, gently press it down with the back of a spoon. Reduce the oven temperature to 375°F (190°C).

Step 5: Whisk the custard

In a medium bowl or large measuring jug, whisk together the eggs, whole milk, heavy cream, Dijon mustard, remaining 1/4 teaspoon salt, and black pepper until evenly combined. Whisk gently rather than beating in lots of air; a smooth mixture makes a more delicate custard.

Measure out 1 cup of the grated cheddar for the filling and reserve the remaining 1/2 cup for the top.

Step 6: Assemble and bake the tart

Spread the cooled onions evenly across the warm pastry shell, then scatter the 1 cup of cheddar over them. Slowly pour in the custard, allowing it to settle between the onions. Sprinkle the reserved 1/2 cup cheddar over the top. Keep the filling just below the pastry rim; if your pan is shallower than specified, do not force in excess custard.

Bake at 375°F (190°C) for 35 minutes. The top should be golden, the edges set, and the center should have only a gentle wobble rather than a liquid ripple. An instant-read thermometer inserted into the center should register 160°F (71°C), without touching the pan. If needed, bake for another 5 minutes and check again. Loosely shield the pastry edges with foil if they brown before the filling is ready.

Step 7: Rest, slice, and serve

Transfer the tart, still in its pan, to a wire rack and let it stand for 20 minutes. This resting time allows the custard to settle so the slices hold together neatly.

If using a removable-bottom pan, carefully remove the outer ring while supporting the base. Cut into 8 wedges and serve warm. A crisp salad of lettuce, cucumber, and radishes with a tangy vinaigrette makes a lovely accompaniment.

Pro Tips

• Keep the pastry cold: If the dough becomes soft or greasy while rolling, refrigerate it for 10 minutes before continuing.
• Give the onions room: A wide skillet encourages moisture to evaporate. A crowded, narrow pan makes the onions steam and take longer to brown.
• Grate the cheddar yourself: Freshly grated cheese melts more smoothly than many packaged shredded cheeses.
• Watch the custard, not just the timer: Ovens and pan materials vary. Aim for a gently set center at 160°F (71°C), not a completely rigid filling that may turn rubbery.
• Choose the right pan depth: A standard shallow tart pan may not hold all the filling. Use the specified deep tart pan or a deep-dish pie plate.

Variations

• Swiss and cheddar: Replace 3 ounces (85 g) of the cheddar with the same weight of Swiss cheese or Gruyère for a slightly nuttier filling.
• Milk-only custard: Replace the 1/4 cup heavy cream with 1/4 cup whole milk, using 1 cup (240 ml) whole milk total. The tart will be a little lighter but still set well.
• Pastry shortcut: Use one refrigerated pie crust large enough to line the specified pan. Chill and blind-bake according to the package directions before adding the filling.

Storage & Make-Ahead

Prepare ahead: Refrigerate the wrapped pastry dough for up to 2 days, or freeze it for up to 2 months and thaw overnight in the refrigerator. The cooked onions can be refrigerated in a covered container for up to 3 days. If the dough is very firm, let it stand at room temperature for 10 minutes before rolling.

Store the baked tart: Refrigerate within 2 hours of baking and keep covered for up to 4 days. For longer storage, wrap individual chilled slices tightly and freeze for up to 2 months. Thaw overnight in the refrigerator.

Reheat: Place refrigerated slices on a baking sheet, cover loosely with foil, and warm at 325°F (165°C) for 20 minutes, or until the center reaches 165°F (74°C). Continue in 5-minute increments if needed. Remove the foil for the final 5 minutes to help refresh the crust.

Nutrition (per serving)

Calories: 411 kcal | Carbs: 25g | Protein: 12g | Fat: 28g | Saturated Fat: 16g | Fiber: 2g | Sugar: 5g | Sodium: 405mg | Cholesterol: 146mg

Nutrition is an estimate for one of eight slices, using the homemade butter pastry and the milk-and-cream custard. Optional salad and extra flour for rolling are not included.