Broccoli Calzones

I love calzones because they're like pizza, only more elegant. Only they're not really all that elegant, because they always turn out misshapen and interesting-looking. Anyway, this is one of my favorite recipes ever.

1 Tablespoon olive oil
1 10-ounce bag frozen chopped broccoli, thawed
2 cloves garlic, chopped
1/8 Teaspoon red-pepper flakes
Flour, for rolling dough
1 loaf frozen bread dough, thawed
1/2 cup part-skim ricotta cheese
1/4 cup grated Parmesan cheese
3/4 cup shredded part-skim mozzarella cheese
Coarse salt and ground pepper
Prepared tomato sauce, (optional)
1/2 medium red onion, finely chopped

In a large nonstick skillet, heat oil over medium. Add onion; cook until softened. Add broccoli, garlic, and pepper flakes. Cook, stirring occasionally, until liquid has evaporated, 5 to 7 minutes. Transfer to a medium bowl; set aside to cool.

Preheat oven to 400 degrees;. Form calzones: Divide dough into 4 equal pieces. On a lightly floured surface, stretch each piece out, first to a 3-by-4-inch oval, then stretch again, this time to a 6-by-8-inch oval. (Let dough rest a few minutes if too elastic to work with.)

Stir cheeses into cooled broccoli mixture; season generously with salt and pepper. Assemble calzones: Spread a rounded 1/2 cup broccoli mixture over half of each piece of dough, leaving a 1/2-inch border; fold over to form a half-moon. Press edges to seal. Transfer to baking sheet.

Bake until golden, about 25 minutes. Serve with tomato sauce, if desired.