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- 1 sheet of puff pastry (thawed) - 3 large onions, thinly sliced - 2 tablespoons olive oil - 1 tablespoon butter - 1 teaspoon fresh thyme leaves - 1 cup grated Gruyère cheese - 2 large eggs - ½ cup heavy cream - 1 teaspoon sugar for caramelizing - Salt and pepper The main ingredients of this tart bring rich flavors together. Puff pastry forms the base. It is flaky and light. Onions add sweetness when cooked well. I like to use three large onions for depth of flavor. Olive oil and butter provide a smooth cooking fat. Fresh thyme gives a herby note that pairs well with cheese. Gruyère cheese is the star, adding creamy, nutty goodness. Eggs and heavy cream create a rich custard. You can add sugar to help caramelize the onions. Salt and pepper are key to balance the taste. {{ingredient_image_1}} Start by slicing your onions thinly. Heat olive oil and butter in a large skillet over medium heat. Once hot, add the onions and a pinch of salt. Stir them often. Cook for about 20 to 25 minutes. You want them soft and golden brown. This slow cooking helps with caramelization. Next, add the sugar and thyme. Stir well and cook for 5 more minutes. The sugar enhances the sweetness of the onions. The thyme adds a fresh, earthy taste. Remove the skillet from heat and let the onions cool slightly. Now, roll out your puff pastry on a floured surface. Aim for a size that fits your tart pan. Gently press the pastry into the pan and trim any excess. This step ensures a nice, even crust. Spread the caramelized onions evenly over the pastry shell. Use a spatula for a smooth layer. In a bowl, whisk together the eggs and heavy cream. Add salt and pepper to taste. Pour this mixture over the onions, covering them well. Finally, sprinkle the grated Gruyère cheese on top. This cheese melts beautifully, adding a rich flavor. Preheat your oven to 400°F (200°C). This high heat helps the tart cook evenly. Bake the tart for 30 to 35 minutes. Look for a golden brown color on top. The filling should be set but still creamy. Once baked, remove the tart from the oven and let it cool for a few minutes. This cooling time helps it firm up before slicing. Enjoy your delicious creation! To achieve the perfect caramelized onion texture, you need patience. Start by slicing your onions thinly. This helps them cook evenly. Heat your skillet to medium and add olive oil and butter. The fat helps with flavor and texture. Cook the onions slowly. This is key! Stir them every few minutes. Low heat allows the sugars in the onions to break down. This takes about 20-25 minutes. You want them soft and golden brown. Add your sugar and thyme at the end. This boosts the sweet flavor. To prevent soggy pastry, make sure your onions cool before adding them to the tart. Excess moisture can ruin the crispiness. Roll out the puff pastry on a lightly floured surface. Aim for an even thickness of about ⅛ inch. This helps it bake evenly. When placing the pastry in the tart pan, press gently. Trim any excess pastry around the edges. This gives a nice clean look and helps with cooking. Garnish your tart with fresh thyme sprigs for a pop of color. This also adds a nice herbal note. Consider pairing the tart with a light salad. A simple green salad with lemon vinaigrette works well. The fresh greens contrast with the rich tart flavors. Enjoy your savory delight! Pro Tips Use Sweet Onions: Opt for sweet onions like Vidalia or Walla Walla for a richer flavor that enhances the caramelization process. Chill the Puff Pastry: Keep the puff pastry chilled until you're ready to bake. This helps achieve a flakier texture when baked. Grate the Cheese Fresh: For the best melting and flavor, grate the Gruyère cheese just before using it rather than buying pre-grated cheese. Let it Rest: Allow the tart to rest for a few minutes before slicing. This helps the filling set and makes for cleaner slices. {{image_2}} You can swap Gruyère cheese for other cheeses. Cheddar adds a sharp flavor. Feta gives a tangy twist. Use what you like best. Herbs and spices can change the taste too. Try rosemary or oregano for a different aroma. A pinch of smoked paprika adds warmth and depth. If you need a gluten-free option, use a gluten-free puff pastry. Many brands offer this now. You can also make a crust with almond flour or oats. For a vegan version, replace eggs and cream with silken tofu and plant milk. Nutritional yeast can give a cheesy flavor. Enjoy a tasty tart without dairy! Adding veggies can make your tart even better. Sautéed mushrooms bring earthiness. Spinach adds color and nutrients. You could also toss in cooked bacon for a smoky touch. It adds richness and pairs well with onions. Want a unique twist? Sprinkle in some cumin or chili flakes. These spices can change the game and make your tart special. To keep your tart fresh, refrigerate it in an airtight container. This helps keep moisture in. Use it within three days for the best taste. When reheating, place slices in a warm oven. Set it to 350°F (175°C) and heat for about 10-15 minutes. This method keeps the crust crispy and the filling warm. Avoid using a microwave, as it can make the pastry soggy. You can freeze the tart before or after baking. If freezing before baking, wrap it tightly in plastic wrap and then foil. This keeps it safe from freezer burn. You can freeze it for up to three months. To bake from frozen, preheat your oven to 400°F (200°C) and add 10-15 minutes to the cooking time. If you freeze it after baking, let it cool completely first. Then wrap it tightly and store it in the freezer. To thaw, place it in the fridge overnight. Reheat in the oven at 350°F (175°C) for about 20 minutes. This way, your tart will taste fresh and delicious. You can prepare this tart ahead of time by making the filling and crust separately. First, caramelize the onions and let them cool. Then, store the onions in an airtight container in the fridge for up to three days. You can also roll out the puff pastry and keep it ready in the fridge. This way, you save time on the day you want to serve it. When ready, simply layer the onions on the pastry, add the egg mixture, and bake. This method keeps flavors fresh and makes serving easy. Yes, you can use different pastries. While puff pastry gives a light and flaky texture, you can try a shortcrust pastry for a sturdier base. You could even use phyllo dough for a crispier bite. If you prefer a gluten-free option, look for gluten-free pastry dough at the store. Each option will change the texture and taste slightly, but they will all work well with the onion and cheese filling. This tart pairs well with a fresh side salad. A simple mixed greens salad with a light vinaigrette works great. You could also serve it with roasted vegetables for added flavor. For drinks, a crisp white wine or sparkling water complements the tart nicely. If you want to go casual, serve it with a nice cup of soup. Each of these options enhances the meal and brings balance to the rich flavors of the tart. This article covered how to make a delicious Caramelized Onion Gruyère Tart. You learned about key ingredients like puff pastry, onions, and Gruyère cheese. We went through easy steps for preparation, assembly, and baking. Tips helped you perfect caramelization and avoid sogginess. In conclusion, you can customize this tart with different cheeses or spices. Enjoy it fresh, or store leftovers for later. Each bite will impress your family and friends. Experiment and make this tart your own!

Caramelized Onion Gruyère Tart

A delicious tart featuring caramelized onions and melted Gruyère cheese, perfect for any occasion.
Print Recipe Pin Recipe
Prep Time 20 minutes
Cook Time 35 minutes
Total Time 1 hour
Course Appetizer
Cuisine French
Servings 8
Calories 300 kcal

Ingredients
  

  • 1 sheet puff pastry (thawed)
  • 3 large onions, thinly sliced
  • 2 tablespoons olive oil
  • 1 tablespoon butter
  • 1 teaspoon fresh thyme leaves
  • 1 teaspoon sugar
  • to taste salt and pepper
  • 1 cup grated Gruyère cheese
  • 2 large eggs
  • 1 cup heavy cream

Instructions
 

  • Preheat your oven to 400°F (200°C).
  • In a large skillet, heat the olive oil and butter over medium heat. Add the sliced onions and sprinkle with salt.
  • Cook the onions, stirring occasionally, for about 20-25 minutes until they are soft and caramelized. Add sugar and thyme, stirring well for an additional 5 minutes. Remove from heat and let cool slightly.
  • Roll out the puff pastry on a floured surface to fit into a tart pan. Gently press it into the pan, trimming any excess.
  • Spread the caramelized onions evenly over the pastry shell.
  • In a bowl, whisk together the eggs, heavy cream, salt, and pepper until combined. Pour the egg mixture over the onions.
  • Sprinkle the grated Gruyère cheese evenly on top.
  • Bake in the preheated oven for 30-35 minutes or until the tart is golden brown and the filling is set.
  • Remove from the oven and let cool for a few minutes before slicing.

Notes

Serve warm, garnished with fresh thyme sprigs, on a wooden board. You can also add a side salad for a refreshing contrast!
Keyword cheese, onions, puff pastry, tart