To prepare a spaghetti sauce with fresh tomatoes recipe, you will first need to gather your ingredients. You will need the following ingredients: 1 pound fresh Italian tomatoes, 1 cup chopped onion, 2 tablespoons chopped garlic, 1/2 cup diced bell pepper, and 1 teaspoon salt. Cook the tomatoes on medium heat until they are soft, about 5 minutes. Remove the peppers from the heat and add the tomato mixture to the onion mixture. Stir the mixture until the ingredients are evenly coated. Add salt and pepper to taste.