- Add butter to a large skillet over medium-low heat. When melted, add onions and stir until well coated in butter.
- When onions are turning transparent, after about 10 minutes of cooking, stir in brown sugar and sherry vinegar.
- Continue cooking for 30 to 40 minutes, stirring every 5 minutes or so, until onions are well caramelized. Stir in salt and pepper.
- Pre-heat oven to 500°F (260°C) and place pizza pan or stone in oven.
- Remove pan or stone from oven and place dough on top. Lightly brush with olive oil.
- Sprinkle Gruyere cheese over the dough. Top with caramelized onions and chopped thyme. Layer shaved or grated Fontina cheese over the top.
- Bake pizza at 500 degrees for about 9 to 11 minutes until the dough is nice and crispy.
- Remove from oven and sprinkle chopped parsley over the top.
If you're new to caramelizing onions, you can check out this caramelized sweet onions recipe or this ultimate how-to blog post for additional tips.
If you like this recipe, try our Caramelized Sweet Onion & Goat Cheese Flatbread Pizza!