If you’re looking to capture the best of summer’s bounty in one irresistible bite, this Beefsteak Tomato Tart with Caramelized Onions & Thyme belongs at the top of your to-cook list. It’s one of my all-time favorites—a golden, flaky puff pastry layered with silky, deeply caramelized onions and crowned with juicy slices of beefsteak tomato, melting cheese, and a fragrant hit of fresh thyme. Whether you serve it as a gorgeous appetizer, a light lunch, or the star of your brunch table, this tart is always met with happy sighs and requests for seconds. Every ingredient gets its moment to shine, and that burst of savory, buttery, tangy-sweet flavor? Unforgettable.
Ingredients You’ll Need
The magic of a Beefsteak Tomato Tart with Caramelized Onions & Thyme is how a handful of simple, fresh ingredients turn into a showstopping dish. Don’t skip or swap anything if you can help it—each ingredient plays an important part, from building deep flavor to creating that crisp, golden base.
- Puff pastry (1 sheet, thawed): Opt for all-butter pastry if you can—it bakes up impossibly flaky and buttery, holding all the toppings beautifully.
- Beefsteak tomatoes (3 large, sliced): Their meaty texture and vibrant flavor are what make this tart shine; choose the ripest ones you can find.
- Onions (2 large, thinly sliced): Slowly caramelized onions add sweet, rich depth and make every bite irresistible.
- Olive oil (2 tablespoons): For sautéing the onions; a good olive oil brings a little peppery brightness.
- Butter (1 tablespoon): Adds a silky richness to the onions, helping them caramelize beautifully.
- Sugar (1 teaspoon): Just a tiny bit—this helps coax the onions into that perfect golden sweetness.
- Balsamic vinegar (1 teaspoon): A splash at the end deepens flavor and adds gentle tanginess.
- Gruyère or Swiss cheese (1 cup, shredded): Melted pockets of nutty, creamy cheese work magic beneath and above the tomatoes.
- Fresh thyme leaves (1 teaspoon, plus more for garnish): Earthy and floral, thyme makes this tart feel utterly special.
- Egg (1, beaten with 1 tablespoon water): Brushed around the pastry edge, it ensures that glorious golden hue.
- Salt and black pepper (to taste): Essentials for bringing all the flavors into focus.
How to Make Beefsteak Tomato Tart with Caramelized Onions & Thyme
Step 1: Caramelize the Onions
Set a large skillet over medium heat and add the olive oil and butter. Once everything’s melted and shimmering, tumble in those thinly sliced onions and let them gently cook, stirring every few minutes. Patience is key—you want to coax out all the natural sweetness, not rush them. After about 20 minutes, add the sugar and balsamic vinegar, stirring for another five minutes until they’re golden, jammy, and smelling like heaven. Season with salt and pepper, then let them cool slightly as you prep the next steps.
Step 2: Prepare the Puff Pastry
Unroll your thawed puff pastry on a lightly floured surface, then transfer it to a parchment-lined baking sheet. Take a sharp knife and lightly score a one-inch border around the edge—be careful not to cut all the way through. This little trick creates a raised, ultra-crispy crust that looks bakery-fancy, with almost zero effort.
Step 3: Build the Tart Layers
Spread your sweet and silky caramelized onions over the pastry, keeping inside the border you created. Sprinkle about half the shredded cheese over the onions, then artfully layer the slices of beefsteak tomato across the surface. The tomatoes will overlap a little, and that’s perfect. Season them with salt, black pepper, and fresh thyme leaves, then finish with the rest of the cheese sprinkled over the top. This is where the tart starts to look truly special.
Step 4: Add the Finishing Touches
Brush the exposed pastry border with your egg wash—just one egg beaten with a splash of water. Don’t skip this! It’s how you get that mouthwatering golden finish when the tart bakes. The tart is now ready for the oven, and your kitchen is about to smell incredible.
Step 5: Bake to Golden Perfection
Bake the tart in your preheated 400°F (200°C) oven for 25 to 30 minutes. The pastry should puff up and turn beautifully golden brown, while the cheese melts and the tomatoes soften just enough. Once baked, scatter over a few extra thyme leaves. This stunning Beefsteak Tomato Tart with Caramelized Onions & Thyme can be served warm or at room temperature—you honestly can’t go wrong.
How to Serve Beefsteak Tomato Tart with Caramelized Onions & Thyme
Garnishes
A light sprinkle of fresh thyme leaves right before serving brings a fresh, fragrant note and a pop of color to your Beefsteak Tomato Tart with Caramelized Onions & Thyme. A tiny drizzle of good olive oil or even a few shavings of extra cheese can really elevate each slice—simple touches that make everything feel extra special.
Side Dishes
I can’t recommend serving this tart with a crisp, lemony green salad enough—the contrast of textures and flavors is just perfect. It also pairs beautifully with a bowl of chilled gazpacho or some herby roasted potatoes if you want a heartier meal. For brunch, a fruit salad or a refreshing glass of sparkling lemonade on the side feels oh-so-right.
Creative Ways to Present
Try cutting the tart into slim strips for an appetizer platter, or serve bite-sized squares as elegant party canapés. If you want a rustic touch, serve the tart directly from a wooden board, scattered with extra herbs and a bowl of marinated olives. However you serve it, your Beefsteak Tomato Tart with Caramelized Onions & Thyme is bound to be the star.
Make Ahead and Storage
Storing Leftovers
Pop any leftover tart into an airtight container and keep it in the fridge for up to three days. The pastry stays fairly crisp, and the flavors actually seem to deepen and mingle even more after a night’s rest.
Freezing
If you’d like to freeze your Beefsteak Tomato Tart with Caramelized Onions & Thyme, let it cool completely first. Wrap individual slices or the whole tart tightly in plastic wrap then foil. When ready to enjoy, thaw in the refrigerator overnight for best results—the puff pastry texture holds up surprisingly well.
Reheating
To reheat, place the tart (or individual slices) on a baking sheet in a 350°F oven for 10-15 minutes. This brings back the golden crispness of the pastry and helps the cheese get wonderfully melty again—almost as good as fresh!
FAQs
Can I use a different kind of tomato?
Absolutely! While beefsteak tomatoes have unbeatable flavor and texture, heirloom varieties or even ripe Roma tomatoes will work beautifully in this tart. Just be sure to pick tomatoes that are juicy but not too watery.
Is it possible to make Beefsteak Tomato Tart with Caramelized Onions & Thyme gluten-free?
Yes! Look for gluten-free puff pastry at specialty stores—just follow the same instructions as the original. The toppings are naturally gluten-free, so you won’t sacrifice any flavor.
What other cheeses can I use besides Gruyère or Swiss?
Fontina, Comté, or even mozzarella are all fantastic options, depending on whether you want a milder or more robust cheesy note. You can also do a little mix to suit your taste.
My pastry didn’t puff up as much—what went wrong?
It’s often a temperature issue—if the pastry gets too warm before baking, it doesn’t puff as dramatically. Make sure your oven is fully preheated and work quickly with chilled pastry for best results!
Can I make Beefsteak Tomato Tart with Caramelized Onions & Thyme ahead of time?
Certainly! You can prepare and assemble the tart a few hours ahead, storing it in the fridge until ready to bake. Fresh from the oven is truly wonderful, but room temperature slices are just as delicious for easy entertaining.
Final Thoughts
Sharing a Beefsteak Tomato Tart with Caramelized Onions & Thyme is one of those simple joys that never gets old. Whether you’re celebrating tomato season or just need a reliable, crowd-pleasing recipe, this tart never disappoints. If you haven’t tried making it yet, I promise it’ll quickly become a favorite in your kitchen, too.
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Beefsteak Tomato Tart with Caramelized Onions & Thyme Recipe
- Total Time: 50 minutes
- Yield: 6 servings
- Diet: Non-Vegetarian
Description
Indulge in the delightful flavors of summer with this Beefsteak Tomato Tart featuring sweet caramelized onions, nutty Gruyère cheese, and fragrant thyme on a flaky puff pastry crust.
Ingredients
Puff Pastry:
1 sheet puff pastry, thawed
Beefsteak Tomatoes:
3 large tomatoes, sliced
Caramelized Onions:
2 large onions, thinly sliced 2 tablespoons olive oil 1 tablespoon butter 1 teaspoon sugar 1 teaspoon balsamic vinegar
Cheese:
1 cup shredded Gruyère or Swiss cheese
Thyme:
1 teaspoon fresh thyme leaves, plus extra for garnish
Egg Wash:
1 egg beaten with 1 tablespoon water Salt and black pepper to taste
Instructions
- Preheat the oven: Preheat the oven to 400°F (200°C).
- Caramelize Onions: In a large skillet, heat olive oil and butter. Cook onions slowly until golden, about 20 minutes. Add sugar and balsamic vinegar, cook for 5 more minutes.
- Prepare Pastry: Roll out puff pastry, transfer to a baking sheet. Score a border. Spread onions, half of the cheese, tomatoes, remaining cheese. Season and brush edges with egg wash.
- Bake: Bake for 25–30 minutes until golden. Garnish with thyme.
- Serve: Enjoy warm or at room temperature.
Notes
- This tart is delicious with heirloom tomatoes or a layer of Dijon mustard for extra flavor.
- Pair with a simple green salad for a light meal.
- Prep Time: 20 minutes
- Cook Time: 30 minutes
- Category: Appetizer, Main Course
- Method: Baking
- Cuisine: French-Inspired
Nutrition
- Serving Size: 1 slice
- Calories: 310
- Sugar: 8 g
- Sodium: 360 mg
- Fat: 20 g
- Saturated Fat: 9 g
- Unsaturated Fat: 11 g
- Trans Fat: 0 g
- Carbohydrates: 27 g
- Fiber: 2 g
- Protein: 8 g
- Cholesterol: 30 mg
