Now, let’s move on to crafting this amazing Savory Caramelized Onion and Gruyère Tart. Follow these simple steps to create a dish that your guests will rave about:

1. Preheat the Oven: Begin by preheating your oven to 375°F (190°C).
2. Cook the Onions: In a large skillet, heat butter and olive oil over medium heat. Add the sliced onions, a pinch of salt, and the sugar. Sauté for about 15-20 minutes, stirring occasionally, until the onions are golden brown and caramelized. Stir in the thyme and remove from heat.
3. Prepare the Crust: While the onions are cooking, fit the pie crust into a tart pan. Prick the bottom of the crust with a fork to prevent bubbling. Place the tart shell in the fridge to chill for about 10 minutes.
4. Pre-bake the Shell: Remove the chilled crust from the fridge and bake it in the preheated oven for about 10-12 minutes until lightly golden. Remove and allow it to cool slightly.
5. Mix the Filling: In a bowl, whisk together the eggs, heavy cream, salt, and pepper. Add the caramelized onions and half of the grated Gruyère cheese to the mixture and stir until combined.
6. Assemble the Tart: Pour the onion and cheese filling into the pre-baked crust. Sprinkle the remaining Gruyère cheese on top.
7. Bake: Place the tart in the oven and bake for 30-35 minutes or until the filling is set and the cheese is bubbly and golden.