Heat one tablespoon olive oil in a large pot over medium-high heat. Add pork and season with salt and pepper. Cook until browned, breaking it into small pieces.
Add garlic, fennel seed, and crushed red pepper flakes. Toast the spices.
Add broth, season, and simmer. Meanwhile, cook pasta until just before al dente.
Add broccoli rabe and pasta to the pot, simmer until rabe is tender. Season with salt, pepper, and more red pepper flakes.
Serve in bowls, topped with cheese. Optionally, squeeze lemon over.
