Prepare the Tomatoes. Slice tomatoes and place them on paper towels. Sprinkle with salt and let them sit for 20-30 minutes to draw out excess moisture. Pat dry.
Par-Bake the Crust. Roll out your pie crust into a 9-inch pie dish and prick the bottom with a fork. Bake for 10 minutes, then cool.
Layer the Ingredients. Start with a layer of tomatoes, then sprinkle with chopped green onions and basil. Repeat the layers.
Mix the Topping. Combine mayonnaise, cheddar, and mozzarella in a bowl. Spread over the top of the tomatoes.
Bake. Bake for 30–35 minutes until golden and bubbly. Let cool slightly before slicing.