Quick Recipe Version (TL;DR)
Quick Ingredients
- Unsalted butter, melted and cooled: 1 cup (226 g)
- Powdered sugar: 1/2 cup (60 g), plus more for dusting
- All-purpose flour: 2 cups (240 g) for crust + 3 tbsp (24 g) for filling
- Cornstarch: 1 tbsp (8 g)
- Fine sea salt: 1/2 tsp for crust + pinch for filling
- Granulated sugar: 1 1/2 cups (300 g)
- Large eggs: 4
- Fresh lemon zest: 2 tbsp (from 3–4 lemons)
- Fresh lemon juice, strained: 3/4 cup (180 ml)
- Optional: 1 tsp vanilla extract (crust)
Do This
- 1. Heat oven to 350°F (175°C). Line a 9×13-inch metal pan with parchment, leaving overhang.
- 2. Whisk butter, powdered sugar, vanilla, and 1/2 tsp salt. Stir in 2 cups flour. Press into pan; dock with a fork.
- 3. Bake crust 18–20 minutes until lightly golden at edges.
- 4. Lower oven to 325°F (163°C). Whisk sugar, 3 tbsp flour, cornstarch, and pinch of salt. Whisk in eggs, then zest and juice.
- 5. Pour over hot crust. Bake 18–22 minutes until center barely jiggles.
- 6. Cool 1 hour on a rack, then chill 1 hour. Dust with powdered sugar, slice into 24 bars.
Why You’ll Love This Recipe
- Bright, tangy lemon custard balanced by a buttery, tender shortbread base.
- Foolproof technique for a silky, sliceable filling without curdling.
- Make-ahead friendly—flavor improves as they chill.
- Simple pantry ingredients, big bake-sale-worthy payoff.
Grocery List
- Produce: 4–5 medium lemons (for 3/4 cup juice and 2 tbsp zest)
- Dairy: 1 cup (226 g) unsalted butter; 4 large eggs
- Pantry: All-purpose flour, granulated sugar, powdered sugar, cornstarch, fine sea salt, optional vanilla extract
Full Ingredients
Shortbread Crust
- Unsalted butter, melted and slightly cooled: 1 cup (226 g)
- Powdered sugar: 1/2 cup (60 g)
- All-purpose flour: 2 cups (240 g)
- Fine sea salt: 1/2 tsp
- Optional: Vanilla extract: 1 tsp
Lemon Custard Filling
- Granulated sugar: 1 1/2 cups (300 g)
- All-purpose flour: 3 tbsp (24 g)
- Cornstarch: 1 tbsp (8 g)
- Fine sea salt: small pinch (about 1/8 tsp)
- Large eggs: 4, room temperature
- Finely grated lemon zest: 2 tbsp (from 3–4 lemons)
- Fresh lemon juice, strained: 3/4 cup (180 ml)
For Finishing
- Powdered sugar for dusting: 1/4–1/2 cup (30–60 g)
Step-by-Step Instructions
Step 1: Prep the pan and preheat
Position a rack in the center of the oven and preheat to 350°F (175°C). Line a 9×13-inch metal baking pan with parchment paper so it overhangs on two sides for easy lifting. Lightly grease the parchment and exposed sides of the pan.
Step 2: Make the shortbread
In a medium bowl, whisk the melted butter, powdered sugar, vanilla (if using), and salt until smooth. Add the flour and stir with a spatula until no dry patches remain; the mixture will be soft and dough-like. Transfer to the prepared pan and press firmly and evenly into a compact layer, reaching all corners. Dock the surface with a fork (about 20 pricks) to prevent puffing.
Step 3: Par-bake the crust
Bake the crust for 18–20 minutes, until the edges are lightly golden and the surface looks set. While the crust bakes, start the filling so it is ready to pour over the hot crust.
Step 4: Mix the lemon custard
Reduce the oven temperature to 325°F (163°C). In a medium bowl, whisk together the granulated sugar, flour, cornstarch, and salt. Whisk in the eggs just until combined—avoid whipping in too much air. Whisk in the lemon zest and strained lemon juice until smooth. For an ultra-smooth custard, pour the mixture through a fine-mesh sieve into a pitcher.
Step 5: Bake the bars
Immediately pour the filling over the hot crust. Return the pan to the oven and bake for 18–22 minutes, until the edges are set and the center wobbles slightly when the pan is gently nudged. There should be no wet liquid sloshing.
Step 6: Cool and chill to set
Transfer the pan to a wire rack and cool at room temperature for 1 hour. Then refrigerate, uncovered, for at least 1 hour (or up to overnight) until cold and fully set. Cooling ensures clean slices and a silky texture.
Step 7: Finish and slice
Use the parchment overhang to lift the slab onto a cutting board. Dust generously with powdered sugar. For the neatest cuts, warm a sharp knife under hot water, wipe dry, and slice into 24 bars (6 by 4). Wipe the blade between cuts. Dust again if needed just before serving.
Pro Tips
- For maximum lemon flavor, rub the lemon zest into the sugar with your fingertips before adding other ingredients—this releases aromatic oils.
- Use a light-colored metal pan; dark or glass pans can overbrown the crust and affect the filling’s set.
- Do not overwhisk the filling. Too much air creates bubbles and a foamy top; a gentle whisk leads to a silky, glossy custard.
- Lowering the oven to 325°F for the custard prevents curdling and keeps the texture smooth.
- Powdered sugar can dissolve in the fridge. Dust just before serving, or use “snow sugar” if you need it to last longer.
Variations
- Meyer Lemon Bars: Swap regular lemons for Meyer lemons for a sweeter, floral profile. Reduce sugar to 1 1/3 cups (267 g) if desired.
- Lemon-Lime Bars: Use 1/2 cup lemon juice + 1/4 cup lime juice; garnish with mixed citrus zest.
- Herbed Shortbread: Add 1–2 tsp very finely chopped fresh thyme or rosemary to the crust for a subtle, savory note.
Storage & Make-Ahead
Refrigerate bars in an airtight container, layered with parchment, for up to 5 days. For longer storage, freeze cut bars on a tray until firm, then wrap individually and store in a freezer bag for up to 2 months; thaw in the fridge and dust with powdered sugar just before serving. The crust can be baked up to 24 hours ahead; cool, cover, and keep at room temperature, then add filling and bake.
Nutrition (per serving)
Approximate per bar (1 of 24): 185 calories; 8 g fat; 28 g carbohydrates; 2 g protein; 95 mg sodium; 20 g sugars.
