1. Heat oil in a large skillet over medium heat. Cook garlic and pepper flakes until tender, about 1 minute. Add greens and cook, stirring until tender, about 5 minutes. Remove from heat and stir in pine nuts and lemon zest and juice. Season with salt.
2. Meanwhile, cook pasta in well-salted water according to package directions. Reserve 1/2 cup pasta water and then drain.
3. Add pasta to skillet, tossing to coat, and add reserved water to adjust consistency. Sprinkle with lemon zest and cheese before serving.