Quick Recipe Version (TL;DR)
Quick Ingredients
- 2 medium zucchini (about 450 g / 1 lb), sliced 1/4-inch thick
- 1 medium eggplant (about 565 g / 1 1/4 lb), sliced 1/4-inch thick
- 3 bell peppers (1 red, 1 yellow, 1 orange), sliced into 1/2-inch strips
- 3 tablespoons olive oil
- 2 teaspoons kosher salt, divided
- 1 teaspoon black pepper, divided
- 15 oz (425 g) ricotta
- 10 oz (285 g) frozen chopped spinach, thawed and squeezed very dry
- 1 large egg
- 2 cloves garlic, finely grated
- 1/2 teaspoon lemon zest
- 12 oven-ready lasagna noodles (about 255 g / 9 oz)
- 12 oz (340 g) low-moisture mozzarella, shredded (about 3 cups), divided
- 3/4 cup (75 g) finely grated Parmesan, divided
- 4 tablespoons (56 g) unsalted butter
- 1/4 cup (32 g) all-purpose flour
- 4 cups (960 ml) whole milk, warmed
- 1/4 teaspoon ground nutmeg
- 1/2 cup fresh basil leaves, for topping
Do This
- 1. Roast zucchini, eggplant, and peppers at 425°F (220°C) until browned and tender (about 25–35 minutes), then blot off moisture.
- 2. Mix ricotta, squeezed spinach, egg, garlic, lemon zest, 1/2 teaspoon salt, and 1/4 teaspoon pepper.
- 3. Make béchamel: melt butter, whisk in flour for 1 minute, then whisk in warm milk; simmer until silky and thick (about 6–8 minutes).
- 4. Assemble in a greased 9 x 13-inch pan: béchamel, noodles, ricotta-spinach, roasted veg, mozzarella, repeat; finish with béchamel and Parmesan.
- 5. Bake at 375°F (190°C) covered 30 minutes, then uncovered 20 minutes until bubbly and browned.
- 6. Rest 20 minutes for clean buffet squares; cut into 16 pieces.
- 7. Top with fresh basil right before serving.
Why You’ll Love This Recipe
- Rainbow layers, buffet-friendly: Roasted vegetables make distinct, colorful layers that slice neatly into squares.
- Comforting but bright: Creamy ricotta-spinach and silky béchamel balance the sweet, roasty vegetables.
- Make-ahead friendly: Roast the vegetables and mix the filling in advance, then bake when you need it.
- No watery lasagna: Roasting and blotting the vegetables concentrates flavor and keeps the layers clean.
Grocery List
- Produce: 2 medium zucchini, 1 medium eggplant, 3 bell peppers (red/yellow/orange), 2 garlic cloves, 1 lemon (for zest), 1/2 cup fresh basil leaves
- Dairy: 15 oz ricotta, 10 oz frozen chopped spinach, 1 large egg, 12 oz low-moisture mozzarella, Parmesan, 4 tablespoons unsalted butter, 4 cups whole milk
- Pantry: Oven-ready lasagna noodles, olive oil, all-purpose flour, kosher salt, black pepper, ground nutmeg
Full Ingredients
Roasted Rainbow Vegetables
- 2 medium zucchini (about 450 g / 1 lb), sliced lengthwise or into rounds, 1/4-inch thick
- 1 medium eggplant (about 565 g / 1 1/4 lb), sliced into planks or rounds, 1/4-inch thick
- 3 bell peppers (1 red, 1 yellow, 1 orange), seeded and sliced into 1/2-inch strips
- 3 tablespoons olive oil
- 1 1/2 teaspoons kosher salt
- 3/4 teaspoon black pepper
Ricotta-Spinach Layer
- 10 oz (285 g) frozen chopped spinach, thawed and squeezed very dry
- 15 oz (425 g) ricotta (whole-milk preferred)
- 1 large egg
- 2 cloves garlic, finely grated or minced
- 1/2 teaspoon lemon zest
- 1/2 teaspoon kosher salt
- 1/4 teaspoon black pepper
- 1/2 cup (50 g) finely grated Parmesan (from the total), optional but recommended for extra savory flavor
Silky Béchamel
- 4 tablespoons (56 g) unsalted butter
- 1/4 cup (32 g) all-purpose flour
- 4 cups (960 ml) whole milk, warmed (warm, not boiling)
- 1 teaspoon kosher salt
- 1/4 teaspoon ground nutmeg
- 1/4 teaspoon black pepper
Assembly
- 12 oven-ready lasagna noodles (about 255 g / 9 oz)
- 12 oz (340 g) low-moisture mozzarella, shredded (about 3 cups), divided
- 1/4 cup (25 g) finely grated Parmesan (from the total), for the top
- 1/2 cup fresh basil leaves, torn or thinly sliced (add after baking)
- 1 teaspoon olive oil or softened butter, for greasing the pan
Step-by-Step Instructions
Step 1: Roast the vegetables to concentrate flavor
Preheat the oven to 425°F (220°C). Arrange two racks in the upper and lower thirds of the oven.
Line 2 large sheet pans with parchment paper. Spread the zucchini and eggplant on one pan and the bell peppers on the other (use a third pan if the vegetables are crowded; crowding can steam them instead of roasting).
Drizzle the vegetables with 3 tablespoons olive oil, then sprinkle with 1 1/2 teaspoons kosher salt and 3/4 teaspoon black pepper. Toss to coat and spread into an even layer.
Roast until tender and browned at the edges, rotating pans and switching rack positions halfway through:
- Zucchini: about 20–25 minutes
- Bell peppers: about 25–30 minutes
- Eggplant: about 30–35 minutes
Let the vegetables cool for 10 minutes, then gently blot any excess moisture with paper towels (this helps the lasagna slice into clean squares).
Step 2: Mix the ricotta-spinach layer
Reduce the oven temperature to 375°F (190°C) for baking the lasagna.
In a medium bowl, combine the squeezed-dry spinach, ricotta, egg, garlic, lemon zest, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper. Stir until evenly mixed.
If using, stir in 1/2 cup (50 g) finely grated Parmesan for a slightly firmer, more savory filling.
Step 3: Make a smooth, silky béchamel
In a medium saucepan over medium heat, melt 4 tablespoons butter. Sprinkle in 1/4 cup flour and whisk constantly for 1 minute (this cooks out the raw flour taste; it should look like a pale, bubbling paste).
While whisking, slowly stream in the warm milk. Keep whisking until completely smooth.
Bring to a gentle simmer, then cook, whisking often, until thick enough to coat the back of a spoon, 6–8 minutes.
Season with 1 teaspoon kosher salt, 1/4 teaspoon nutmeg, and 1/4 teaspoon black pepper. Remove from heat.
Step 4: Set up your pan for clean buffet squares
Lightly grease a 9 x 13-inch (23 x 33 cm) baking dish with 1 teaspoon olive oil or a thin layer of softened butter.
Spoon about 1/2 cup béchamel into the bottom and spread it into a thin layer. This helps prevent sticking and encourages even cooking with oven-ready noodles.
Step 5: Assemble neat, colorful layers
Build the lasagna in 3 layers (the exact order matters less than even distribution, but this pattern makes distinct rainbow stripes):
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Layer 1: Place 4 oven-ready noodles in a single layer (overlap slightly if needed). Spread on 1/3 of the ricotta-spinach mixture. Add 1/3 of the roasted vegetables (aim for a mix of zucchini, peppers, and eggplant). Sprinkle with 1 cup (about 4 oz / 115 g) mozzarella. Drizzle with about 1/2 cup béchamel.
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Layer 2: Repeat with 4 noodles, 1/3 ricotta-spinach, 1/3 vegetables, 1 cup mozzarella, and 1/2 cup béchamel.
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Layer 3: Repeat with the final 4 noodles, remaining ricotta-spinach, and remaining vegetables.
Pour the remaining béchamel evenly over the top (use a spoon to push sauce into corners). Finish with the remaining 1 cup mozzarella and 1/4 cup (25 g) Parmesan.
Step 6: Bake until bubbling and golden
Cover the dish tightly with foil (try not to let the foil touch the cheese; a little tenting helps).
Bake at 375°F (190°C) for 30 minutes.
Remove the foil and bake for 20 minutes more, until the top is golden and the edges are bubbling.
For extra browning, broil on High for 1–2 minutes, watching closely so the top doesn’t burn.
Step 7: Rest, slice into squares, and finish with basil
Set the lasagna on a cooling rack and let it rest for 20 minutes. This resting time is the key to clean buffet squares.
Cut into 16 squares (a 4 x 4 grid). Top with fresh basil right before serving so it stays bright and fragrant.
Pro Tips
- Blot the roasted vegetables: Even well-roasted zucchini and eggplant can carry moisture. A quick blot keeps the béchamel silky (not watery) and helps the squares hold their shape.
- Warm milk = smoother béchamel: Cold milk can make the sauce take longer to thicken and increases the chance of lumps.
- Spread to the edges: Make sure sauce and fillings reach the corners so the outer pieces aren’t dry.
- Rest before cutting: If you cut right away, the layers will slide. Resting makes the buffet squares look sharp and tidy.
- For very clean cuts: Use a long knife and wipe it between slices.
Variations
- Tomato-basil twist: Add 1 cup (240 ml) marinara as a thin layer under the top béchamel, then finish with basil.
- Extra protein: Add 1 (15 oz) can cannellini beans, drained and rinsed, tucked into the veggie layers for a heartier (still vegetarian) square.
- Gluten-free: Use gluten-free lasagna noodles and swap the béchamel flour for a 1:1 gluten-free all-purpose blend.
Storage & Make-Ahead
Refrigerate: Cool completely, then cover and refrigerate for up to 4 days. Reheat individual squares in the microwave for 1–2 minutes or rewarm in a 350°F (175°C) oven until hot (about 15–20 minutes).
Freeze: Wrap squares tightly and freeze for up to 2 months. Thaw overnight in the refrigerator before reheating, or bake from frozen (covered) at 350°F (175°C) for 35–45 minutes until hot in the center.
Make-ahead options: Roast the vegetables up to 2 days ahead and refrigerate. You can also assemble the entire lasagna, cover, and refrigerate for up to 24 hours before baking (add 10 minutes to the covered bake time if baking straight from the fridge).
Nutrition (per serving)
Approximate per 1 of 16 squares: 260 calories, 13 g protein, 22 g carbohydrates, 14 g fat, 4 g fiber, 520 mg sodium. (Values vary by brands and exact vegetable sizes.)
