Preheat the oven to 450 degrees F (230 degrees C).

Melt butter in a skillet over medium heat. Add leeks; cook until tender. Spread evenly into bottom of pie crust.

Toss Swiss cheese, Romano cheese, and flour together in a bowl; spread over leeks.

Beat heavy cream and eggs together in a separate bowl; pour over cheese layer. Top with tomato slices; season with salt and black pepper.

Bake in the preheated oven for 15 minutes. Reduce the oven temperature to 325 degrees F (165 degrees C); continue baking until crust is lightly browned and a knife inserted into center comes out clean, about 30 minutes.