Steps
1. Preheat the oven to 400°F (200°C).
2. Thinly slice the onion.
3. Heat the olive oil in a skillet over medium heat. Add the sliced onion and cook until softened and golden brown, about 10-15 minutes.
4. Sprinkle the sugar over the caramelized onions and cook for an additional 2-3 minutes until the sugar has melted and the onions are slightly caramelized.
5. Season with salt and pepper to taste.
6. Roll out the puff pastry on a lightly floured surface and transfer it to a baking sheet.
7. Spread the caramelized onions evenly over the puff pastry, leaving a border around the edges.
8. Crumble the goat cheese over the onions.
9. Bake in the preheated oven for 20-25 minutes until the pastry is golden brown and the cheese is melted and bubbly.
10. Garnish with fresh thyme leaves before serving.