Arrange the sliced tomatoes on paper towels to drain excess moisture. Season the tomato slices with a sprinkle of salt. Let sit for 30 minutes.

Preheat your oven to 350°F (175°C).

If using a store-bought pie crust, follow the package instructions for pre-baking. If making your own pie crust, roll it out, place it into a 9-inch pie dish, and crimp the edges for a decorative finish. Line your pie crust with parchment paper and add pie weights or dried beans to keep the crust from puffing up. Bake in the oven for about 10-15 minutes until the edges start to brown. Remove from oven, let cool for a few minutes, and add ingredients.

In a bowl, combine the cheeses, mayonnaise, garlic powder, oregano, black pepper, and red pepper flakes or cayenne pepper. This mixture will form the creamy filling for your pie.

Begin assembling the pie by spreading a layer of the cheese mixture over the pre-baked pie crust.

Next, layer the seasoned tomato slices, chopped onions, and basil on top of the cheese mixture.

Spread the creamy filling evenly over the tomato slices, ensuring it covers them completely. Repeat assembly and then top off the pie with the last of the creamy cheesy filling.

Bake the tomato pie in the preheated oven for about 40 minutes or until it's golden and bubbly.

Once done, remove the pie from the oven and allow it to cool for at least 30 minutes before slicing.

Serve the tomato pie warm or at room temperature. Garnish with fresh basil leaves and additional grated Parmesan, if desired.