1. Preheat oven to 425°F. In a large frying pan, heat 2 tablespoons of olive oil. Add onion and cook over medium-low heat, stirring often, until very soft, about 10 minutes. Add garlic and rosemary and cook 2 minutes. Remove from heat and let cool 5 minutes. In a small bowl, combine hot pepper flakes with remaining 1 tablespoon oil.
2. Unroll pizza dough and place on a lightly oiled baking sheet. With fingers, press dimples into dough. Brush with hot pepper oil. Sprinkle chicken over dough. Spoon cooked onions over chicken. Sprinkle cheese on top.
3. Bake about 20 minutes, until dough is crisp and golden brown and cheese is melted. Let cool slightly. Cut into lx2-inch rectangles. Serve in a napkin-lined basket.