This undeniably delicious yet easy heirloom tomato tart is one of the first recipes I shared on my first food blog over eight years ago. After making this tart again today, I was reminded of why I love it so much (and also, why I love baking!) But, don't feel like you have to stick to the recipe. The recipe below is for a "Summer in Provence" version of a tomato tart, as it features some French favorites: Gruyere cheese, herbs de Provence and Dijon mustard. Feel free to substitute any of these. Sharp cheddar can be used instead of Gruyere; dried or fresh oregano or basil for the herbs de Provence, and any type of mustard can be used. Why "heirloom tomatoes" you may ask? They have more flavor! But you can definitely swap them out for regular tomatoes so that you can enjoy this tart all year long-- even after the heirloom tomatoes' very short season is over.
Since the filling is liquid (egg and heavy cream), I par-baked the pie crust to ensure that the bottom of the crust stayed crisp. [For novice bakers, par-baking a pie crust simply means you line a pay plate with dough, add foil and the pie weights, then bake until the bottom dries out. You then remove the pie weights and bake until it's just starting to turn golden. By half-way baking or "par" baking, you ensure that the bottom can withhold the liquid filling.]
Once the crust is par-baked, it's smooth sailing. I smeared Dijon mustard along the bottom, sprinkled Gruyere cheese and dried herbs de Provence, then topped that with my eggs and cream whisked together. Lastly, I lined tomato slices on tops. Some overlapped-- some didn't. It was fine either way! I baked it at 375 F until the filling had completely set--it didn't wobble at all was browned in some areas. I let it cool on a cooling rack before cutting it, which made for a clean cut. It was so good that I nearly ate half the tart!
Heirloom Tomato Tart Recipe
4 large heirloom tomatoes, cored and cut into 1/4 inch thick rounds
2 tablespoons Dijon mustard
1 par-baked 9-inch tart crust*
1 cup grated Gruyere cheese
1 teaspoon dried herbs (OK to use basil, thyme, oregano, or my favorite- "herbes de Provence")
2 large eggs
1/4 cup heavy cream
1 teaspoon salt
1/2 teaspoon freshly ground black pepper.
Additional herbs to sprinkle on top, if desired (fresh or dried OK - basil, thyme, oregano or "herbes de Provence")
*If you use a pie pan or ready-made pie crust, which is deeper than a tart pan, you will need to increase the quantity of the custard (the eggs + heavy cream), and the bake time (longer bake time will be needed).
Preheat oven to 375 F. Put the tomato slices in a colander, and place it in the sink. Let the tomatoes sit for 15 minutes to drain off any excess liquid.
Spread the mustard evenly over the par-baked tart shell. Sprinkle the grated cheese over the mustard, and sprinkle the dried herbs over the cheese.
Whisk the eggs in a small bowl, or a large measuring cup with a spout, to break up the yolks. Whisk in the cream, salt, and pepper. This is your custard. Pour the custard evenly over the bottom of the tart crust. You may have to swish it around to get it to cover the bottom.
Working from the outside in, lay the drained tomato slices in slightly overlapping concentric circles, making sure the tart is covered in tomato slices.
Place the tart on the center rack in the oven, and bake at 375 F until the custard is set, about 35-40 minutes. (Set custard won't jiggle when you shake the pan and will be firm when you touch it). The tomatoes in this tart may give off a hot liquid--don't confuse this with uncooked eggs and overcook your tart. The liquid will evaporate as the tart cools.
Remove the tart from the oven and set it on a wire rack. Allow the tart to cool slightly before serving. You can enjoy this tart warm or at room temperature.
Serving suggestion: Serve this tart alongside a simple arugula salad with a homemade vinaigrette.