Preheat oven to 375 degrees F and line a half sheet baking sheet with parchment paper
Take one frozen puff pastry sheet out of the freezer and allow it to come to room temperature for 10 minutes or until soft enough to unroll
Place the puff pastry on the lined baking sheet and sprinkle with gruyere cheese and thyme leaves leaving ½ inch board on the puff pastry
Layer the sliced onions (slightly overlapping) over the cheese
Using a pasty brush, egg wash the boarder of the puff pastry, fold over the edges and press down using a fork
Bake the French Onion Tart for 45-50 minutes or until the puff pastry is golden brown and the onions are cooked through
Remove the tart from the oven and serve warm!
Serving: 1serving | Calories: 121kcal | Carbohydrates: 9g | Protein: 3g | Fat: 8g | Saturated Fat: 3g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 4g | Trans Fat: 1g | Cholesterol: 16mg | Sodium: 77mg | Potassium: 51mg | Fiber: 1g | Sugar: 1g | Vitamin A: 64IU | Vitamin C: 2mg | Calcium: 53mg | Iron: 1mg