Heat water for pasta in large pot, and add 1 teaspoon of salt to the water. Once boiling, add pasta and cook according to package directions. Once pasta is done, reserve ½ cup of pasta water and set aside. Then strain pasta and pour back in pot.
While the water is boiling, melt butter into a large pan and heat on low-to-medium until butter has melted. Stir in shrimp, garlic, red pepper flakes and season with pepper and remaining teaspoon of salt. Cook shrimp until pink, about 5-7 minutes.
Add tomatoes, Italian seasoning and spinach, and cook another 2-3 minutes, stirring occasionally.
Transfer shrimp mixture into the pot with the pastaand stir in parmesan, parsley, pasta water and milk. Heat another 3-5 minutes on low, until warmed throughout.
Cook your pasta al dente because it will cook a few minutes more when combined with shrimp and sauce, anyway.
IF your pasta is ready way before the shrimp mixture, rinse the cooked pasta in cold water in a strainer right away to avoid sticking.
To defrost frozen shrimp: place shrimp in a colander in the sink and run cold water over them for 10-15 minutes.
Dab thawed shrimp dry before cooking to remove excess moisture, which can impact searing.
When is shrimp done? Overcooked shrimp can be chewy...yuk. Shrimp is fully cooked when it has an opaque, pinky color.
For softer tomatoes...add them to the pot earlier, when cooking the shrimp.