1. Cold water
Rinse the stain with cold water (hot water makes the stain permanent). Hold the t-shirt inside out under the water tap.
2. Treat with lemon juice
Use a sponge and spot treat the white t-shirt gently with lemon juice. Lemon juice is only for white fabrics, then wash in the washing machine.
3. Sun dry
Let the t-shirt dry in the sun. If there are still spots left from the tomato sauce, the sun will act as a natural bleach.