Heat oil in a 12-inch cast-iron or other large heavy skillet over medium-high heat. Add sausage and onion; cook, stirring occasionally, until the sausage is browned, 3 to 4 minutes. Add orzo and garlic; cook, stirring, for 1 minute more.
Stir in broth, crushed red pepper, and salt. Bring to a boil. Stir in broccolini (or broccoli). Reduce heat, cover and simmer until the orzo is tender, 8 to 10 minutes. Uncover and continue cooking until the broth is absorbed.
Stir in Parmesan and lemon zest. To serve, top with additional Parmesan and crushed red pepper, if desired.
2 starch, 2 vegetable, 1 medium-fat protein, 1/2 fat