Tomato, Onion and Gruyere Tart

It’s only right that I offer you a “savory tart” loves…❤️

Fresh, juicy and plump tomatoes from the backyard vine top onions caramelized with fresh thyme and umami-rich anchovies (optional), and a layer of nutty and slightly sweet gruyere cheese. And importantly, all easily prepared with frozen prepared puff pastry. Jump on this tomato tart while summer tomatoes are in season.

I used heirloom tomatoes for my tomato tart primarily because they were convenient. I'm growing them. They add a nice pop of color, but don't feel compelled to do the same. Any ripe red tomatoes will work just fine. Cherry tomatoes sliced in half will work too.

The Savory Tart leans toward "cooking" and not so much "baking", and I am a huge proponent of streamlining where possible with prepared ingredients. And conveniently, the folks at Pepperidge Farm and Dufour Pastry Kitchens are my go-to for prepared frozen puff pastry. No guilt here! (I did however take a class in making puff pastry many years ago. Something like 27 steps to produce a perfect sheet of puff pastry.... that's not happening. Ya think?)

Serving Suggestions:

I've been making this tomato tart pretty much the same for decades and it never fails to be met with approval, not to mention that it presents so nicely. It has been served it at showers, sliced in thin wedges as an appetizer for a pool party, for Sunday brunch, and have even packed it for a concert in the park.

Consider serving it alongside some of my other favorites:

• Buttermilk Cucumbers with Almonds and Everything
• Arugula and Orange Salad with Serrano Ham in Citrus Dressing
• Asparagus Mimosa
• Chilled Cucumber, Avocado and Tomatillo Soup

Ingredients

• prepared frozen puff pastry
• Dijon mustard
• yellow onions
• olive oil
• garlic cloves
• balsamic vinegar
• chopped thyme
• anchovy fillets
• fresh tomatoes, preferably heirloom
• salt
• Gruyère cheese
• fresh basil

See recipe card for quantities.

Instructions

Preheat oven to 375°F.

Place thawed puff pastry on a floured surface or a piece of parchment.

Roll out puff pastry to 11” square. 

Transfer puff pastry to 9.5” tart pan, pushing pastry up edges and folding overhang toward the center, pressing against side of pan. Pierce the bottom of the crust with a fork several times.

Place in the refrigerator for 30 minutes. 

Line the pastry with parchment and fill with pie weights. Or, using foil, form the foil to serve as an insert to retain the pastry shape. (See photo in blog instructions.) Bake for 12 minutes.

Remove from oven and remove parchment/pie weights or foil. Bake for 5 more minutes. 

Once cool, brush the bottom of the pastry with Dijon mustard. Reserve

Heat oil in a large skillet over medium heat. Add onion, stirring occasionally, until softened and lightly caramelized, about 20 minutes. 

Stir in garlic, anchovies (if using), thyme and salt, and stir to combine until fragrant, about one minute. Add balsamic vinegar and cook down completely. Reserve.

Place sliced tomatoes on a paper towel. Sprinkle with salt. Cover with another paper towel and press down lightly. (This will remove moisture from the tomatoes.) Allow to rest for 15 minutes.

Spread onion mixture evenly over pastry shell.

Top evenly with cheese.

Arrange tomato slices in concentric circle over cheese. Season with salt and pepper.

Bake tart in the middle of the oven for 50 minutes, or until pastry is golden. Cool on a rack.

Remove rim of tart pan for serving if desired and sprinkle with chopped basil.

Hint: Caramelizing onions can take a bit of stovetop patience to get them just right. It requires cooking the onions consistently at medium heat for at least 20 minutes to render the natural sugars found in onions. The result is well worth the wait resulting in something perfectly flavorful.

Because of the time involved, I try to make batches of caramelized onions, put them in zipper bags and freeze them. They are great to have on hand for topping a pizza, stuffed into a grilled cheese, melted into a cheeseburger, or tossed into pasta.

Substitutions

• Tomatoes - I used heirloom tomatoes, but any good red slicing tomato will work equally as well. Use cherry tomatoes sliced in half. Or a mix of tomatoes.
• Cheese - Substitute cheddar, Swiss, fontina, Comte, manchego or even mozzarella
• Vegetarian - This is vegetarian -- and a great option for all to enjoy
• Fresh Thyme - substitute a scant ½ teaspoon dried thyme

Variations & Additions

• Make it piquant - Top the tart with capers -- or fried capers. Frying capers is easy. Heat a few teaspoons of olive oil in a small skillet over medium-hight heat. Add two tablespoons of well-drained capers to the skillet and saute for about five minutes until they are lightly browned and crispy. Drain on a paper towel.
• Make it Italian - Replace the thyme in the onions with oregano and use mozzarella cheese
• Nicoise - Slice 3-4 hard-boiled eggs and layer into the tart. Top the tart with sliced Nicoise olives
• Prosciutto, Peppers and Olives - Add ¼ cup diced jarred roasted red peppers to the onions. Tear 1.5 oz. of prosciutto into small pieces and layer in between the cheese and the tomatoes. Top the tomatoes with slivered olives: I like Castelvetrano, but Kalamata olives will work well too.
• Make it Spicy -- Add a few pinches of red pepper flakes to the onions when the thyme is added. Drizzle the tart lightly with Calabrian chili oil. (Yum!)
• Make it Sweet and Spicy -- Instead of the balsamic vinegar, add a few teaspoons of sugar to the caramelized onions. Drizzle the top of the tart lightly with hot honey. (Yum!)

Equipment

• 9.5" tart pan with removable bottom
• Large skillet (12")

Storage

This is best served shortly after baking, or at room temperature. It will keep in the refrigerator for up to five days.

Warm it on a baking sheet in the oven at 250°F for about 15 minutes -- until the cheese melts.

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Tomato, Onion and Gruyere Tart

The Savory Tart

Fresh, juicy and plump tomatoes from the backyard vine top onions caramelized with fresh thyme and umami-rich anchovies (optional), and a layer of nutty and slightly sweet gruyere cheese. And importantly, all easily prepared with frozen prepared puff pastry.

Print Recipe Pin Recipe

Prep Time 30 minutes mins

Cook Time 45 minutes mins

Resting time 30 minutes mins

Total Time 1 hour hr 45 minutes mins

Course Appetizer, brunch, Main Course, Side Dish

Cuisine American

Servings 6

Equipment

• 9.5" tart pan
• 12" skillet

Ingredients

  

• 1 sheet of prepared frozen puff pastry from a 17.3 oz. package, thawed
• 1 tablespoon Dijon mustard
• 2 large yellow onions thinly sliced
• 2 tablespoons olive oil
• 2 cloves garlic minced
• 1 teaspoon fresh chopped thyme
• 2 anchovy fillets minced optional
• 1 tablespoon balsamic vinegar
• 1-½ pounds heirloom tomatoes
• salt
• 8 ounces Gruyère cheese shredded (about 2 cups)
• Fresh basil for garnish

Instructions

 

• Preheat oven to 375°F.
• On a lightly floured surface or a piece of parchment, roll out puff pastry to 11” square. Transfer to 9.5” tart pan, pushing pastry up edges and folding overhang toward the center, pressing against side of pan. Pierce the bottom of the crust with a fork several times. Place in the refrigerator for 30 minutes.
• Line the pastry with parchment and fill with pie weights. Or, using foil, form the foil to serve as an insert to retain the pastry shape. (See photo in blog instructions.) Bake for 12 minutes. Remove from oven and remove parchment/pie weights or foil. Bake for 5 more minutes. Once cool, brush the bottom of the pastry with Dijon mustard. Reserve
• Heat oil in a large skillet over medium heat. Add onion, stirring occasionally, until softened and lightly caramelized, about 20 minutes. Add garlic, anchovies (if using), thyme and salt, and stir to combine until fragrant, about one minute. Add balsamic vinegar and cook down completely. Reserve.
• Place sliced tomatoes on a paper towel. Sprinkle with salt. Cover with another paper towel and press down lightly. (This will remove moisture from the tomatoes.) Allow to rest for 15 minutes.
• Spread onion mixture evenly over pastry shell and top with cheese. Arrange tomato slices in concentric circle over cheese. Season with salt and pepper.
• Bake tart in the middle of the oven for 50 minutes, or until pastry is golden. Cool on a rack. Remove rim of tart pan for serving if desired and sprinkle with chopped basil.

Keyword #caramelized onion tart, #fresh produce, #fresh tomatoes, #onion tart, #puff pastry, #savory tart, garden recipes, tomato tart