2 tablespoons olive oil
1/2 yellow onion, minced (optional)
2 large cloves garlic, sliced
1-28oz can crushed tomatoes (see below for my favorite crushed tomatoes)
2 tablespoons tomato paste (optional)
1/2 cup broth or water
1 teaspoon salt
1/4 teaspoon pepper
Pinch of red pepper flakes
1/2 cup reserved pasta water (if making pasta)
Heat olive oil and add onion, salt and the pepper. Cook the onions until they are just beginning to turn golden brown.
Add the garlic and cook until fragrant. Add the tomato paste if you have any.
Add the rest of the ingredients and cook until bubbling. Reduce the heat and simmer for 15 minutes.