Parmesan Shrimp Pasta

In a large pot of salted boiling water, cook penne until al dente. Drain, reserving 1/2 cup pasta water, and return to pot. Meanwhile, in a large skillet, melt butter. Add garlic and cook until fragrant, 1 minute. Add red pepper flakes and shrimp and season with salt and pepper. Cook until shrimp is pink, 1 to 2 minutes per side. Add parsley and combine. Set shrimp aside on a plate (keep juices in skillet). To skillet, add spinach and season with salt. Let wilt, 2 minutes, then add tomatoes, heavy cream, 1/4 cup pasta water, and Parmesan and simmer, 5 minutes. Add shrimp and cooked penne and stir until combined. (If you want it more saucy, add remaining 1/4 cup pasta water.) Garnish with Parm and serve.