Add the tomato sauce, tomato paste, Italian seasoning, and sugar to a small saucepan and whisk to combine. Bring the sauce to a gentle boil over medium/high heat. Reduce the heat to simmer for 5 minutes.

Remove the saucepan from the heat and use it immediately. Otherwise, let the sauce cool and store the sauce in an airtight container in the refrigerator for up to 7 days.