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A slice of savory onion tart on a plate, showcasing the layers of caramelized onions and melted Gruyère cheese.
FL Recipes

Caramelized Onion Tart: The Ultimate Guide to Savory Perfection

Discover the secret to the richest, most savory Caramelized Onion Tart. This recipe features a foolproof method for deeply sweet onions, nutty Gruyère cheese, and a perfectly flaky, buttery crust. An impressive and delicious appetizer or light meal.
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Prep Time 20 minutes
Cook Time 1 hour 10 minutes
Total Time 1 hour 30 minutes
Servings: 8 slices
Course: Appetizer, Lunch, Main Course
Cuisine: American, French
Calories: 320
Ingredients Equipment Method Nutrition Notes

Ingredients
  

  • 1 9-inch pie crust store-bought or homemade, puff pastry or shortcrust
  • 2 tbsp unsalted butter
  • 1 tbsp olive oil
  • 3 large yellow onions thinly sliced
  • 1 tsp balsamic vinegar
  • 1 tsp fresh thyme leaves
  • 1 cup Gruyère cheese shredded
  • 1 large egg
  • 1/2 cup heavy cream
  • 1/2 tsp salt
  • 1/4 tsp black pepper

Equipment

  • 1 9-inch tart pan with removable bottom
  • 1 Large Skillet

Method
 

  1. Preheat your oven to 400°F (200°C). Press your pie crust into a 9-inch tart pan. Prick the bottom with a fork and blind bake for 15 minutes until lightly golden. Set aside. Reduce oven temperature to 375°F (190°C).
  2. While the crust bakes, melt butter and olive oil in a large skillet over medium-low heat. Add the sliced onions and salt. Cook slowly, stirring occasionally, for 45-50 minutes, until the onions are deeply caramelized, soft, and jammy.
  3. Stir the balsamic vinegar and fresh thyme into the onions and cook for one more minute. Remove from heat.
  4. Spread the caramelized onions evenly over the bottom of the par-baked crust. Sprinkle the shredded Gruyère cheese over the onions.
  5. In a separate bowl, whisk together the egg and heavy cream. Season with salt and pepper. Gently pour the egg mixture over the onions and cheese in the tart pan.
  6. Bake for 20-25 minutes at 375°F (190°C), or until the filling is set and the top is golden brown.
  7. Let the tart cool in the pan for at least 10 minutes before removing the outer ring, slicing, and serving.

Nutrition

Calories: 320kcalProtein: 9gFat: 24gFiber: 2g

Notes

Tip 1: Don't overcrowd the pan when cooking the onions. If necessary, use two skillets to ensure they caramelize rather than steam.
Tip 2: Feel free to substitute Gruyère with other cheeses like goat cheese, feta, or even a sharp white cheddar for a different flavor profile.
Keyword caramelized onion tart,onion tart,savory tart

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