In a large pot of salted poiling water, cook penne until al dente. Drain, Reserve 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
Add 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.)