French Onion Tart: A Savory Delight with Caramelized Onions and Cheese

Introduction
This French Onion Tart is a perfect combination of sweet caramelized onions, savory cheese, and buttery puff pastry. It’s an easy yet elegant dish that can be served as an appetizer, side dish, or even a light meal. The addition of Gruyère cheese makes it even more indulgent, while the crispy puff pastry provides a delightful texture.

Ingredients
1 sheet puff pastry, thawed
2 large Vidalia onions, thinly sliced
2 tablespoons unsalted butter
1/2 cup beef stock
1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried thyme)
1/4 cup grated Gruyère or Swiss cheese
Salt and pepper to taste
1 egg, beaten (for egg wash)
How to Make
1. Preheat the Oven: