Rustic Tomato and Onion Tart with Fresh Thyme

By AislePrompt Test Kitchen · Reviewed by AislePrompt Editorial · Published 2026-05-03 · Updated 2026-05-03

A flaky, buttery tart layered with ripe tomatoes, caramelized onions, and fragrant fresh thyme, perfect for a light brunch or appetizer. This french-inspired brunch (vegetarian) ready in about 75 minutes pairs all-purpose flour, cold, cubed unsalted butter, ice water for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 260 calories and feeds 6, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart.

Ingredients

• 1 1/4 cups all-purpose flour
• 6 tbsp cold, cubed unsalted butter
• 3 tbsp ice water
• 1 medium (about 6 oz), thinly sliced yellow onion
• 1 tbsp olive oil
• 2 medium (about 10 oz), thinly sliced ripe tomatoes
• 1 tsp fresh thyme leaves
• 1 tsp, divided salt
• 1/2 tsp black pepper
• 1/4 cup grated Parmesan cheese
• 1 large, beaten (for egg wash) egg

Instructions

1. Step 1: In a medium bowl, combine 1 1/4 cups all-purpose flour and 1/4 tsp salt. Add 6 tbsp cold unsalted butter cubes and use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.
2. Step 2: Slowly add 3 tbsp ice water, 1 tbsp at a time, mixing gently until the dough just comes together. Form into a disk, wrap in plastic, and chill for at least 30 minutes.
3. Step 3: While dough chills, heat 1 tbsp olive oil in a skillet over medium heat. Add 1 medium thinly sliced yellow onion and 1/2 tsp salt. Cook, stirring occasionally, for 15 minutes until the onions are golden and caramelized. Remove from heat.
4. Step 4: Preheat oven to 400°F. On a floured surface, roll out the dough into a 12-inch circle. Transfer to a parchment-lined baking sheet.
5. Step 5: Spread the caramelized onions evenly over the dough, leaving a 2-inch border.
6. Step 6: Arrange 2 medium thinly sliced ripe tomatoes over the onions. Sprinkle with 1 tsp fresh thyme leaves, 3/4 tsp salt, 1/2 tsp black pepper, and 1/4 cup grated Parmesan cheese.
7. Step 7: Fold the edges of the dough over the filling, pleating as needed. Brush the crust with 1 beaten egg.
8. Step 8: Bake for 30-35 minutes until the crust is golden and crisp, and the tomatoes are tender. Let cool 10 minutes before slicing.