Preheat oven at 400 F.
Cut eggplants into 1/3-inch thick slices and grill them on medium-high heat for 3 to 4 minutes, until slightly charred on each side.
Meanwhile, prepare the sauce. Mince onion and cook it in olive oil for a few minutes. When it turns golden in color, add tomato purée, salt, and pepper. Simmer on low heat for at least 10 minutes, but the longer the better. If you want, you can skip this step and use store-bought marinara sauce.
Cover the bottom of a 9x9-inch baking pan with a couple tablespoons of tomato sauce.
It’s time to compose the Parmigiana. Layer the different components following this order: grilled eggplant slices, tomato sauce, basil leaves, diced mozzarella and Parmesan cheese. You should have enough ingredients to make around 5 layers.
Bake for 15 to 20 minutes, until bubbling and slightly golden.
Once ready, let it stand for 10 minutes before serving. If you want, you can garnish with some more basil leaves.
