1 pound frozen pizza dough, thawed and at room temperature
Cornmeal, for sprinkling
1 small red onion, half thinly sliced and half chopped
Kosher salt and freshly ground black pepper
3/4 teaspoon crushed red pepper flakes
1/2 cup grated Parmesan
5 tablespoons extra-virgin olive oil
3 garlic cloves, minced
1 1/2 teaspoons sweet paprika
3 tablespoons tomato paste
6 ounces 80 percent lean ground beef
6 ounces frozen collard greens, thawed and drained
Grated zest of 1 lemon (about 1 tablespoon)
2 teaspoons fresh lemon juice