- 1 tablespoon olive oil, plus extra for brushing
- 2 tablespoons butter
- 2 large yellow onions, thinly sliced
- 2 large cloves garlic, very thinly sliced
- 1 tablespoon chopped fresh rosemary
- 1 (13.8 ounce) package refrigerated pizza dough, or 1 sheet frozen puff pastry, thawed
- 1/3-1/2 pound Fontina cheese, shredded
Heat a large sauté pan over medium heat.
Add oil, butter, onions and garlic. Season with salt and pepper. Stir frequently until onions are golden and very tender, about 25-30 minutes.
Meanwhile, preheat oven to 450°F.
On a lightly floured cutting board, roll pizza crust or puff pastry into a rectangle, approximately 15x12 inches in size. Cut in half lengthwise to form 2 long, thin rectangles.
Transfer to a parchment-lined baking sheet and brush lightly with olive oil. If using puff pastry, poke all over with a fork.
Stir rosemary into onions, then divide between 2 tarts. Spread along length of crust, leaving a small border at edges. Top with Fontina.
Bake for 10-12 minutes, or until golden (puff pastry may take slightly longer). Cool slightly, then cut crosswise into strips before serving.
Serve warm or at room temperature.