Preheat oven to 350°F (175°C).
Slice tomatoes and sprinkle with salt. Let them drain on paper towels for 10 minutes to remove excess moisture.
Layer the tomatoes into the pre-baked pie crust. Sprinkle pepper, chopped green onions, and basil over the tomatoes.
In a bowl, mix the mozzarella, cheddar, and mayonnaise together.
Spread the cheese mixture evenly over the top of the pie.
Bake for 30-35 minutes or until the top is golden and bubbly.
Cool slightly before slicing and serving.