In a medium saucepan, cook onion and garlic in hot oil until tender, about 5 minutes. Add seasoning, tomatoes, salt, pepper, and sugar, if desired, stirring to combine. Bring to boiling; reduce heat. Simmer, uncovered, for 10 minutes, stirring occasionally. Remove from heat; cool slightly.
Transfer tomato mixture to a blender container or food processor bowl. Cover and blend or process until smooth. Toss with desired cooked pasta. Use within 1 day, or freeze up to 1 month.
Spoon finished food into ice cube trays. Cover with waxed paper and freeze until firm. When ice cubes are frozen, remove cubes from tray and store in a resealable plastic freezer bag or freezer container. Label package with contents and date. Use within 1 month. Before serving, let thaw in the refrigerator overnight.
Heat thawed mixture to lukewarm in a small dish set in a pan of hot water. Stir before serving. Always sample a small bite to make sure the food is not too hot.