In a large pot of boiling salted water, cook orecchiette according to package instructions. During the last 2 minutes of cooking, blanch broccoli rabe. Remove broccoli rabe, and reserve 1 cup cooking water. Drain pasta and set aside.

In a large skillet over medium heat, heat oil. Add sausage and cook, stirring occasionally, until warmed through and slightly golden, about 5 minutes. Add 1 tablespoon butter and garlic and season with a generous amount of black pepper. Cook until fragrant, about 1 minute.

Add about ½ cup reserved pasta water and bring to a simmer. Add remaining 2 tablespoons butter then add broccoli rabe and pasta, tossing to combine.

Add Parmesan, lemon juice and zest, and red pepper flakes. Toss constantly until cheese is melty, removing skillet from heat when about half the cheese has melted. If sauce is too thick, loosen with more pasta water. Season with salt.