Heat the olive oil in a large skillet over medium heat.

Add the chopped onion and cook for about 3 minutes until softened.

Stir in the garlic and cook for another minute.

Pour in the tomato passata along with about ¼ cup of water to rinse the bottle.

Season with salt and pepper.

Reduce the heat to medium-low and simmer for 30–40 minutes, stirring occasionally, until the sauce becomes thick and rich.

Preheat the oven to 430°F (220°C).

Line three baking trays with parchment paper.

Wash and dry the eggplants, remove the stems, and slice them into ¼-inch rounds.

Arrange the slices in a single layer.

Brush both sides lightly with olive oil and sprinkle with salt.

Bake for about 25 minutes until lightly golden. Rotate the trays halfway through cooking if necessary for even roasting.

Preheat the oven to 350°F (180°C).

Spread a thin layer of tomato sauce over the bottom of a baking dish.

Arrange the first layer of roasted eggplant.

Cover with tomato sauce.

Sprinkle with Parmesan cheese, mozzarella, and fresh basil.

Repeat the layering process until you have four layers of eggplant.

Finish with a generous amount of tomato sauce, Parmesan, and mozzarella on the top layer. Leave the basil off the final layer.

Bake the Eggplant Parmigiana for about 30 minutes until the cheese is melted and bubbling.

Allow it to rest for at least 15 minutes before slicing.

Garnish with fresh basil and serve warm.