Place linguine pasta, cherry tomatoes, sliced onion, minced garlic, Better than Bouillon (if using), 1 teaspoon salt (increase to 2 teaspoons if not using boullion), ground black pepper and red pepper flakes in a wide low pot or skillet.
Add 4 ½ cups water and make sure the pasta is completely submerged.
Bring the mixture to a boil, stirring and tossing the pasta with tongs frequently, until the pasta is al dente and most of the water has evaporated, about 8-9 minutes.
At this stage add raw shrimp and baby spinach. Keep tossing with tongs for a few more minutes, until spinach is wilted and shrimp is pink and cooked through.
Taste and season with salt and pepper, if needed.
Divide into 4 bowls and serve with freshly grated parmesan (if you want)