Preheat the oven to 450°F (230°C).
In a skillet over medium heat, melt butter and sauté leeks until tender. Spread evenly into the bottom of the pie crust.
Combine Swiss cheese, Romano cheese, and flour in a bowl. Spread this mixture over the leeks.
In another bowl, beat together heavy cream and eggs. Pour the mixture over the cheese layer.
Top with tomato slices and season with salt and black pepper.
Bake for 15 minutes, then reduce heat to 325°F (165°C). Continue baking until the crust is lightly browned and a knife inserted in the center comes out clean, about 30 minutes.
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