Grease a large frying pan (large enough to hold all the cod in a single layer) with 2 Tablespoons olive oil and fry the garlic and onion over medium heat until golden. Add tomato sauce and mix well. Add 1 teaspoon sugar and 1/2 teaspoon salt. Thicken sauce by cooking for 30 minutes on a low simmer, stirring occasionally.
Place the cod loins in a single layer on the tomato sauce in the pan. Cook on a low simmer for 6-8 minutes on each side. Chop red peppers and add to the sauce. Cook for a few more minutes. If sauce is too thick add in a little bit of vegetable broth or water.