1. Bring 4 qt. water to a boil in a large Dutch oven. Add 2 tsp. kosher salt, return to a boil, and stir in broccoli rabe. Cook 1 minute or until crisp-tender; drain. Plunge into ice water to stop cooking process; drain.
2. Cook pasta in Dutch oven according to package directions; drain, reserving 1/2 cup hot pasta water.
3. Melt butter with oil in Dutch oven over medium heat; add garlic, and sauté 1 to 2 minutes or until tender. Add red pepper and lemon zest; cook, stirring constantly, 1 minute. Stir in broccoli rabe; cook, stirring constantly, 1 minute. Stir in hot cooked pasta, reserved pasta water, Parmesan, and lemon juice; cook 1 to 2 minutes. Season with kosher salt and black pepper. Top with cheese.
The Power of Pasta Water Before you drain off your perfectly cooked pasta (al dente, of course!), scoop out at least 1 cup of that rich, starchy pasta water to make an easy pan sauce. We used 1/4 to 1/2 cup in most of the dishes here, but for most recipes save a little extra in case you want a looser sauce. The cloudy broth marries with butter or oil for silky, creamy results. And because you've cooked your pasta with a proper amount of salt (about 1 Tbsp. kosher salt per quart of water), the leftover liquid delivers flavor too. Use it whenever you feel saucy.