Beefsteak Tomato Tart with Caramelized Onions
A rustic French-inspired savory tart featuring a buttery, flaky homemade crust filled with silky caramelized onions, fresh beefsteak tomato slices, and a creamy gruyere-thyme custard. The combination of sweet caramelized onions, bright tomato, and rich cheese creates layers of sophisticated flavor balanced by herbaceous thyme. The crust is made from scratch using a food processor for a tender, delicate texture that shatters when cut. This elegant yet approachable dish works equally well for weeknight dinner or entertaining guests. It celebrates summer tomatoes at their peak and showcases how simple, quality ingredients transform into something memorable. The broiled cheese top adds a golden finish and slight char that the entire tart. Perfect for lunch, light supper, or as part of a vegetable-focused menu.
Ingredients
- 1 ¼ cup all-purpose flourwhole wheat pastry flour0.9:1baking
whole wheat adds nuttiness, slightly denser crumb
- 8 tablespoon unsalted butter
- ½ teaspoon salt
- 1 teaspoon granulated sugar
- 5 tablespoon non-fat milkwater1:1dairy-free
slightly less tender crust
- ½ pound beefsteak tomato
- 3 tablespoon olive oil
- 1 onion
- ½ cup heavy cream
- 2 teaspoon fresh thyme leaves
- 2 clove garlic
- 1 teaspoon kosher salt
- ½ teaspoon freshly ground black pepper
- 1 cup gruyere cheeseemmental1:1cheesedairy-free
similar melting, slightly milder flavor
- fresh basil(optional)
Instructions
- 1
Combine flour, salt, and sugar in food processor. Add butter and pulse until pea-sized pieces form.
- 2
Add milk one tablespoon at a time, pulsing until dough forms a rustic ball.
- 3
Shape dough into a disk on a floured surface. Wrap and refrigerate 1 hour.
- 4
Preheat oven to 400 degrees F.
- 5
Allow dough to sit unwrapped on a floured board until pliable, about 15 minutes.
- 6
Roll dough into a large circle with a floured rolling pin, turning a quarter turn with each roll. Roll to 1/4-inch thickness.
- 7
Transfer dough to a 9-inch tart pan with removable bottom. Press into sides, leaving 1/2 inch excess at edge. Trim excess with rolling pin against pan edge. Chill 30 minutes.
- 8
Poke fork holes throughout crust bottom. Cover with foil and top with pie weights or uncooked beans. Bake 15-20 minutes until edge is light golden.
- 9
Remove weights and foil. Return to oven and bake 5-10 minutes more. Cool on rack. Keep oven at 400 degrees F.
- 10
Heat olive oil in saute pan over medium-low heat. Add onion and cook, tossing every few minutes. Once translucent, reduce heat to low. Cook 20-25 minutes until caramelized. Season with salt and pepper. Set aside.
- 11
Heat remaining olive oil in a small saute pan. Cook garlic and thyme until fragrant, about 30 seconds.
- 12
Add heavy cream and increase heat until reduced by half. Stir in gruyere cheese.
- 13
Pour cream mixture into prepared crust. Top with caramelized onions and tomato slices. Sprinkle remaining gruyere cheese on top.
- 14
Bake 10-15 minutes until tart is hot and cheese is melted.
- 15
Place under broiler for 5 minutes. Garnish with fresh basil.
Tips
Chill the assembled tart shell multiple times during preparation. Cold dough shrinks less and produces a more tender, flaky crust. The initial 1-hour refrigeration and 30-minute pre-bake chill are essential, not optional shortcuts.
Low, slow heat is key to caramelizing onions properly. Rushing with high heat produces bitter, burnt edges rather than sweet, golden caramel. The full 20-25 minutes develops complex flavor that defines this dish.
Pierce the crust generously with a fork before blind baking to prevent excessive puffing. Use actual pie weights rather than beans for even browning and better structural support during the initial bake.
Good to Know
Cover cooled tart loosely with foil. Refrigerate up to 2 days. Reheat gently in a 350 degree F oven for 10-15 minutes until warmed through.
Prepare tart crust dough up to 2 days ahead; wrap and refrigerate. Caramelize onions up to 1 day ahead; store in airtight container. Blind bake crust up to 8 hours ahead. Assemble and bake final tart no more than 2 hours before serving.
Serve warm or at room temperature with a simple green salad dressed in vinaigrette, crusty bread, or alongside roasted vegetables. Pairs well with light rosé, white burgundy, or crisp sauvignon blanc.
Common Mistakes
Do not skip the second chill before blind baking to avoid excessive shrinkage and puffing during initial bake.
Do not rush caramelizing onions on high heat to avoid burnt, bitter onions instead of sweet, golden ones.
Do not overbake the final tart to avoid a tough, rubbery filling; aim for just-melted cheese.
Substitutions
Dairy-Free Swaps
similar melting, slightly milder flavor
General Alternatives
FAQ
Can I make the tart crust ahead?
Yes. Prepare dough up to 2 days ahead and refrigerate wrapped in plastic. You can also blind bake the crust up to 8 hours ahead, cool completely, and store covered at room temperature before adding filling.
What if I don't have a tart pan with a removable bottom?
Use a 9-inch pie pan instead. Line with parchment before rolling dough in, allowing easier removal. Alternatively, bake directly in the pie pan; serve from the pan or slide onto a flat plate while warm.
Can I freeze this tart or make it ahead?
Blind bake the crust and freeze up to 1 month. Thaw before filling. The assembled baked tart keeps refrigerated for 2 days. Freeze the baked tart up to 3 weeks; reheat covered in a 350 degree F oven for 20-25 minutes.