Before you dive into layering, a few simple preparations will ensure your Heirloom Tomato Gratin Lasagna turns out perfectly. These initial steps set the stage for a delightful meal that’s both light and satisfying.

• Preheat the oven to 375°F (190°C). This ensures your lasagna starts baking immediately at the correct temperature for even cooking.
• Prepare the creamy ricotta filling: In a medium bowl, thoroughly stir together the part-skim ricotta cheese, large eggs (lightly beaten), 1/4 cup of chopped fresh basil, 2 teaspoons of grated garlic, 1/4 teaspoon of kosher salt, and 1/4 teaspoon of black pepper. The eggs act as a binder, ensuring the ricotta layer sets beautifully, while the basil and garlic infuse the cheese with aromatic flavors.
• Set the mixture aside. This allows the flavors to meld slightly while you prepare the tomatoes.

Preparing the tomatoes properly is crucial for achieving the perfect balance of flavor and preventing your lasagna from becoming watery. Heirloom tomatoes can be quite juicy, so a little attention here goes a long way.

• Seed the tomatoes: Carefully remove and discard the seeds from about one-third of your tomato slices. If your tomatoes are exceptionally seedy or very juicy, it’s wise to deseed up to one-half of them. This step helps manage the moisture content in the lasagna, ensuring it sets nicely without becoming watery.
• Season the tomatoes: In a large bowl, combine all the tomato slices (both deseeded and undeseeded). Drizzle with 1/4 cup of extra-virgin olive oil, add 1 tablespoon of red wine vinegar (or white wine vinegar for a milder tang), the remaining 2 teaspoons of grated garlic, the remaining 1 teaspoon of kosher salt, and the remaining 1/2 teaspoon of black pepper.
• Toss gently to combine: Use your hands or a large spoon to gently toss the tomatoes, ensuring they are evenly coated with the oil, vinegar, and seasonings. This marinade will infuse the tomatoes with incredible flavor as they bake.

Now comes the fun part: assembling your Heirloom Tomato Gratin Lasagna. The layering technique is straightforward and ensures a harmonious blend of flavors and textures in every slice.

• Prepare your baking dish: Lightly coat a 13- x 9-inch glass or ceramic baking dish with cooking spray. This prevents sticking and makes for easier serving.
• First tomato layer: Arrange one-third of the seasoned tomato slices in a single, even layer on the bottom of the prepared baking dish. These will form the flavorful foundation.
• First noodle layer: Top the tomatoes with 3 no-boil lasagna noodles. Don’t worry if they don’t fit perfectly; you can break them slightly to cover the surface.
• Ricotta layer: Evenly spread all of the prepared ricotta mixture over the lasagna noodles. This creamy layer will add richness and moisture.
• Second noodle layer: Place another 3 lasagna noodles directly over the ricotta.
• Second tomato layer: Arrange another one-third of the tomato slices in a single layer over these noodles.
• Final noodle layer: Top with the remaining 3 lasagna noodles.
• Final tomato topping: Arrange the remaining tomato slices over the top. If necessary, shingle them slightly to create a beautiful, overlapping pattern.
• Add juices: Pour any remaining tomato juices from the mixing bowl evenly over the entire lasagna. These juices are packed with flavor and will help the noodles soften.
• Initial bake: Cover the baking dish tightly with aluminum foil and bake in the preheated 375°F (190°C) oven for 35 minutes. Covering the lasagna helps steam the noodles and cook the tomatoes without browning the top too quickly.

While your lasagna is in its initial bake, you can prepare the crispy, flavorful topping. This crunchy goodness is sprinkled on top for the final ten minutes in the oven, adding a delightful textural contrast.

• Prepare the breadcrumbs: Place the whole grain bread, torn into pieces, into a food processor.
• Pulse until coarse crumbs form: Pulse 4 to 5 times, or until you have coarse, textured breadcrumbs. Avoid over-processing to prevent them from becoming too fine.
• Heat oil: Heat the remaining 2 tablespoons of extra-virgin olive oil in a large skillet over medium heat.
• Toast breadcrumbs: Add the prepared breadcrumbs to the skillet. Cook, stirring frequently, until they are golden brown and toasted, which should take about 3 to 4 minutes. Watch them carefully to prevent burning.
• Cool the breadcrumbs: Transfer the toasted breadcrumbs to a medium bowl and allow them to cool for about 5 minutes. This prevents the cheese from melting too quickly when added.
• Mix in cheese and basil: Once slightly cooled, add the 1/2 cup of freshly grated Parmigiano-Reggiano cheese and the remaining 1/4 cup of fresh basil to the breadcrumbs.
• Toss to combine: Toss everything together until the cheese and basil are evenly distributed throughout the crunchy breadcrumbs. This topping adds a wonderful savory depth and a satisfying crunch to the gratin.

The final steps bring your Heirloom Tomato Gratin Lasagna to golden, bubbling perfection, culminating in a dish that’s ready to be savored.

• Uncover and add topping: After the initial 35 minutes of baking, carefully remove the lasagna from the oven and remove the foil. Evenly sprinkle the prepared breadcrumb mixture over the top of the lasagna.
• Final bake: Return the baking dish to the oven, now uncovered, and continue to bake at 375°F (190°C) until the breadcrumb topping is beautifully golden brown and crispy, typically about 10 minutes. This final bake adds that irresistible gratin crunch.
• Rest before serving: This step is crucial! Let the lasagna rest for about 10 minutes before slicing and serving. Resting allows the layers to set, making it easier to cut neat portions and ensuring the flavors have a chance to fully meld together.