- Preheat oven to 350˚.
- Heat a medium sauté pan with olive oil and butter. Add red onion, season with herbs de Provence and a little salt and pepper. Cook until slightly caramelized, stirring occasionally. While onions are cooking, place sliced tomatoes in a single layer on several folded paper towels, sprinkle with remaining salt. Let stand for approximately 10 minutes. Once onions are cooked, remove from heat and let cool.
- Unroll pie crust and place on a nonstick baking sheet. Spread with Dijon mustard leaving about a one inch boarder on the crust. Sprinkle half the cheddar and half the provolone cheese on crust then top with half the cooked onions. Repeat with next layer keeping the one inch border all the way around the pie dough. Arrange tomato slices in overlapping pattern on top of onion and cheese.
- Fold edges of dough toward center; tucking and pressing to seal (dough will only partially cover tomatoes). Brush folded edge with beaten egg. Place in oven and bake for 35 minutes or until crust is golden brown.
Click here for an instructional cooking video.
Source of recipe: Rebecca Egsieker, The Dairy Chef