Quick answer: To remove a fresh tomato sauce stain, lift off the excess, rinse from the back, then pretreat with warm water, white vinegar, and a little dish soap. Wash right away and check the stain before drying, because heat can set the red pigment.
The fastest way to remove a fresh tomato sauce stain is to lift off the solids, pretreat with dish soap and white vinegar, then wash the garment as soon as possible. Tomato sauce is easier to remove when it is still fresh, so do not let it dry if you can avoid it.
After pretreating, wash the garment according to the care label. If the fabric can handle it, a detergent with enzymes is a strong choice because it helps break down the food residue left behind. For stubborn fresh stains, a powdered oxygen bleach booster can help in the wash.
Always inspect the stain before putting the item in the dryer. Heat can lock in tomato pigment and make the stain much harder to remove. If any red color remains, repeat the pretreat and wash steps instead of drying.
For lingering red pigment, treat the area with hydrogen peroxide on washable fabrics, then air dry and rewash if needed. Another option is to soak the item in hot water with powdered oxygen bleach overnight, then rinse and wash again.
If the fabric is delicate, brightly dyed, or labeled dry clean only, professional cleaning is the safest route.
Or ask about any laundry or garment care question