Place the sliced tomatoes on paper towels. Sprinkle with salt and pepper.
Mix both cheeses and mayonnaise together.
Place the first layer of tomatoes in the pie shell, completely covering the bottom. Cut a tomato slice in half to completely cover the bottom if need be. Sprinkle with a third of the green onions and basil, and spread a third of the cheese mixture on top.
Repeat with two more layers. On the final layer, be sure to let the tomatoes show through the cheese.
Bake for 30 minutes or until the cheese is melted and bubbling.