1. Preheat oven to 400 degrees Fahrenheit.
2. In a frying pan over medium heat, heat oil. Add onion slices and sauté for 20–30 minutes, until soft and golden.
3. Line a cookie sheet with Gefen Parchment Paper. Place puff pastry on the cookie sheet.
4. Arrange the tomatoes in a circle in the middle of the puff pastry sheet. Add the onions on top. Sprinkle with salt and pepper.
5. Trim the edges of the puff pastry to create a circle, leaving about one and a half inches on the sides. Fold over the edges to create a rim.
6. Sprinkle cheese over the onions and tomatoes.
7. Bake for 20 minutes.