Start a pot of salted water and cook pasta according to package directions.

While pasta is cooking, heat olive oil and butter in a large skillet or sauté pan over medium flame. Add garlic and crushed red pepper, and cook for about 1 to 2 minutes, stirring frequently to avoid burning or browning. Turn off heat under pan.

When pasta is cooked, drain, reserving about 1/2 cup pasta water, and add pasta to the skillet with garlic and crushed red pepper. Turn on heat again to medium and add lemon juice and zest, and parsley to the pan. Season lightly with salt and generously with black pepper, and toss everything to combine. Add about 1/4 cup pasta water to the pan and toss. If the pasta looks dry, add a little more pasta water.