Caprese Tomato Pie

Ingredients

1 tablespoon olive oil
1 medium onion, chopped
3 garlic cloves, thinly sliced
1 large beefsteak tomato, 10 ounces, cut into 7 (1/4-inch) thick slices
4 medium assorted color tomatoes, 1 1/2 pounds, cut into 1/4-inch thick slices
6 ounces whole milk mozzarella, shredded, 1 1/2 cups
1/3 cup + 2 tablespoons grated Parmesan cheese
12 fresh basil leaves
3/4 teaspoon salt, divided
1/4 teaspoon ground black pepper, divided
2 large eggs, lightly beaten
1 cup heavy cream
1/3 cup panko breadcrumbs
2 tablespoons unsalted butter, melted

Directions

1. Preheat the oven to 350°F. 
2. Heat the oil in a 10 1/2-inch frying pan over medium heat. Add the onion and cook, stirring occasionally, until slightly softened, 4 minutes. Add the garlic and cook until the onions start to brown, about 2 minutes longer. Transfer to a bowl. Let the skillet cool 5 minutes. 
3. Arrange the beefsteak tomato slices in an overlapping layer over the bottom of the skillet. Top with 1/2 cup of the mozzarella, 1 tablespoon of the Parmesan cheese, 6 basil leaves, 1/4 teaspoon of the salt, and 1/8 teaspoon of the pepper. Repeat with the layering with half of the medium tomato slices, 1/2 cup of the mozzarella, 1 tablespoon of the Parmesan cheese, the remaining 6 basil leaves, 1/4 teaspoon of the salt, and remaining 1/8 teaspoon pepper. Top with the remaining tomato slices and mozzarella. 
4. Combine the eggs, heavy cream, and remaining 1/4 teaspoon salt in a small bowl. Pour over the tomatoes. In a separate bowl combine the remaining 1/3 cup Parmesan cheese, breadcrumbs, and butter; sprinkle over the tomatoes. 
5. Bake in the center of the oven until the breadcrumb mixture has lightly browned and the custard has set, about 50 to 60 minutes. Remove from the oven and let cool at least 30 minutes before slicing. Garnish with additional basil if desired.