Step 1

Set a rack in center of oven; preheat to 450°F. Divide dough in half. On a floured surface, roll out each dough half to a 12 x 6-inch rectangle. Transfer both to a lightly oiled baking sheet. Sprinkle with rosemary; drizzle with 1 tablespoon olive oil. Bake 10 to 12 minutes or until golden.

Step 2

Meanwhile, in a 12-inch skillet heat 2 tablespoons olive oil over medium heat. Add onion and black pepper. Cook 10 minutes or until tender and light brown, stirring occasionally. Add greens and vinegar; toss to coat. Cook 3 to 5 minutes or until greens are wilted and liquid has evaporated.

Step 3

Divide cooked greens between flatbreads; top with cheese. Bake 5 minutes or until cheese is melted. Top with sliced prosciutto before serving.