Beefsteak Tomato Tart with Caramelized Onions & Thyme
Beefsteak Tomato Tart with Caramelized Onions & Thyme

Indulge in the rich flavors of summer with this Beefsteak Tomato Tart with Caramelized Onions & Thyme. This dish combines the sweetness of caramelized onions, the juiciness of beefsteak tomatoes, and the aromatic touch of thyme, all nestled in a flaky, buttery crust. Perfect for a light lunch or a sophisticated appetizer, this tart is sure to impress your guests.
For more savory tart ideas, check out this Easy Rustic Tomato Cheese Tart Recipe or explore the Heirloom Tomato Ricotta Tart for a delightful twist.
Ingredients

- 1 sheet puff pastry, thawed
- 2 large beefsteak tomatoes, sliced
- 2 large onions, thinly sliced
- 2 tablespoons olive oil
- 1 tablespoon butter
- 1 teaspoon sugar
- 1 tablespoon fresh thyme leaves
- Salt and pepper to taste
- 1 cup shredded mozzarella cheese
- 1/4 cup grated Parmesan cheese
- 1 egg, beaten (for egg wash)
Step-by-Step Instructions
1. Caramelize the Onions
Heat the olive oil and butter in a large skillet over medium heat. Add the sliced onions and cook, stirring occasionally, until they begin to soften. Sprinkle with sugar and continue cooking, stirring frequently, until the onions are golden brown and caramelized. This should take about 20-25 minutes. Stir in the thyme leaves and season with salt and pepper. Set aside to cool.
2. Prepare the Puff Pastry
Preheat your oven to 375°F (190°C). Roll out the puff pastry sheet on a lightly floured surface to fit your tart pan. Transfer the pastry to the pan and trim any excess edges. Prick the base of the pastry with a fork to prevent it from puffing up too much during baking.
3. Assemble the Tart
Spread the caramelized onions evenly over the puff pastry. Arrange the beefsteak tomato slices on top of the onions, slightly overlapping them. Sprinkle the shredded mozzarella and grated Parmesan cheese over the tomatoes. Brush the edges of the pastry with the beaten egg to create a golden crust.
4. Bake the Tart
Place the tart in the preheated oven and bake for 25-30 minutes, or until the pastry is golden brown and the cheese is bubbly and lightly golden. Remove from the oven and let it cool for a few minutes before slicing.
Expert Tips
- Choose Ripe Tomatoes: For the best flavor, use ripe but firm beefsteak tomatoes. They should be juicy but not overly soft.
- Evenly Slice the Onions: Thinly and evenly sliced onions will caramelize more uniformly, ensuring a sweet and flavorful base for your tart.
- Prevent a Soggy Crust: To avoid a soggy bottom, you can blind bake the puff pastry for 10 minutes before adding the toppings.
- Add Fresh Herbs: Garnish the tart with additional fresh thyme or basil leaves before serving for an extra burst of flavor.
FAQ
Can I make this tart ahead of time?
Yes, you can prepare the tart a few hours ahead of time and store it in the refrigerator. Reheat it in the oven at 350°F (175°C) for about 10 minutes before serving to restore its crispiness.
What can I serve with this tart?
This tart pairs beautifully with a simple green salad or a refreshing Peach Tomato Caprese Salad. It also makes a great addition to a brunch spread.
Can I use a different type of cheese?
Absolutely! While mozzarella and Parmesan work wonderfully, you can experiment with other cheeses like Gruyère or goat cheese for a different flavor profile.
Enjoy your Beefsteak Tomato Tart with Caramelized Onions & Thyme, a dish that celebrates the vibrant flavors of the season!

Beefsteak Tomato Tart with Caramelized Onions & Thyme
Ingredients
Method
- Heat the olive oil and butter in a large skillet over medium heat. Add the sliced onions and cook, stirring occasionally, until they begin to soften. Sprinkle with sugar and continue cooking, stirring frequently, until the onions are golden brown and caramelized. This should take about 20-25 minutes. Stir in the thyme leaves and season with salt and pepper. Set aside to cool.
- Preheat your oven to 375°F (190°C). Roll out the puff pastry sheet on a lightly floured surface to fit your tart pan. Transfer the pastry to the pan and trim any excess edges. Prick the base of the pastry with a fork to prevent it from puffing up too much during baking.
- Spread the caramelized onions evenly over the puff pastry. Arrange the beefsteak tomato slices on top of the onions, slightly overlapping them. Sprinkle the shredded mozzarella and grated Parmesan cheese over the tomatoes. Brush the edges of the pastry with the beaten egg to create a golden crust.
- Place the tart in the preheated oven and bake for 25-30 minutes, or until the pastry is golden brown and the cheese is bubbly and lightly golden. Remove from the oven and let it cool for a few minutes before slicing.






