Place everything into your pot or large deep pan: the pasta, onions, garlic, tomatoes, 2 cups of spinach, basil, salt, pepper and crushed red pepper flakes. Add in the olive oil and then add in the water.
Bring everything to a high boil and then, turn down the heat to medium and begin mixing everything up together using tongs. Continue mixing and stirring constantly the entire time the pasta is cooking so your pasta noodles don't stick together.
Let the pasta cook for about 10 to 12 minutes (depending on what type of pasta you are using). During the last few minutes of cooking, add the remaining 3 to 4 cups of spinach and mix to combine. Taste, season with more salt and pepper if desired and garnish with some freshly grated parmesan cheese. Serve and enjoy.