Melt butter in a skillet over medium heat; sauté leeks until tender. Spread evenly into bottom of pie crust.
STEP 3
Toss Swiss cheese, Romano cheese, and flour together in a bowl; spread over leeks.
STEP 4
Beat heavy cream and eggs in a separate bowl; pour over cheese layer. Top with tomato slices; season with salt and pepper.
STEP 5
Bake for 15 minutes. Reduce heat to 325°F (165°C); continue baking until crust is lightly browned and knife inserted in center comes out clean, about 30 minutes.