In a medium bowl, combine the diced tomatoes, including the juice from the can, the tomato paste, olive oil, basil, oregano, sugar, garlic, and salt. Whisk together so the tomatoes become soft and everything is well incorporated. Taste and add more salt, if desired.
Use immediately, or store in a tightly covered container in the refrigerator for up to 5 days, or freeze for up to 2 months. Bring to room temperature before using.