Step 1

Wash rapini (see recipe note); drain and coarsely chop.

Step 2

Heat a large pot of salted water to boil. Add rapini and cook 1 minute (working in batches if necessary); transfer rapini to colander to drain. Return water to boil.

Step 3

Add pasta to boiling water and cook according to package directions until al dente (tender, but firm to the bite). Drain pasta reserving 1 cup of the pasta water.

Step 4

Meanwhile, heat oil in a large skillet over medium heat. Add sausage and brown, breaking up with a spoon, 6 to 8 minutes. Add garlic and red pepper flakes; cook and stir until garlic is fragrant and golden, about 1 minute more. Add broccoli rabe and toss to coat. Add pasta and stir to combine, adding reserved cooking liquid a few tablespoons at a time as needed to moisten. Season to taste with salt and pepper. Divide among 4 pasta bowls; sprinkle with parmesan cheese and serve.