Heat the oven to 425°F. Fit the unbaked crust into a 9-inch pie plate, prick the bottom with a fork, line it with parchment, and add pie weights or dried beans.

Blind-bake the crust for 10–15 minutes, until it is just beginning to brown. Remove the weights and let the crust cool slightly.

Slice the tomatoes about 1/4 inch thick. Arrange them on paper towels or a clean kitchen towel, sprinkle generously with salt, and let them stand for 20–30 minutes; blot very thoroughly.

In a bowl, combine the mayonnaise, Cheddar, mozzarella, Parmesan, black pepper, and optional garlic powder.

Layer half of the tomatoes in the partially baked crust. Add half of the green onions and basil, then spread half of the cheese mixture over the top.

Repeat with the remaining tomatoes, green onions, basil, and cheese mixture. Sprinkle the optional additional cheese over the top.

Reduce the oven temperature to 350°F. Bake for 35–45 minutes, until the filling is bubbling and the top is golden brown.

Cool the pie for at least 15–20 minutes before slicing. This resting time lets the creamy filling set and makes cleaner portions possible.