Scrape off any solid pieces of the salsa (including seeds, chunks of vegetables and sauce) as much possible from the cloth using a butter knife or a spoon, without smearing it or embedding it further into the fabric. Avoid using a sharp knife or any other such instrument as it may damage your clothing.
Now run excess of cold water through the back of the stain as soon as possible to force the remains of the salsa back out through the fabric. Do not run the water through the front of the stain as it will only mess up the things for you.
Apply liquid detergent directly to the stained portion of the fabric, and rub it gently in a circular motion, starting from the outside of the stain.
Keep rubbing the detergent on the stained area for 2 to 3 minutes, or until no salsa stain is left in the cloth. Wash the cloth under running water and hang it in the open air to allow the sun to dry it.
If you can still see any remains and the fabric is white or colourfast, apply a mild bleaching agent, like hydrogen peroxide, white vinegar or lemon juice to the stained area. (Never use any of these bleaching agents when treating a coloured cloth as all of them will bleach out colours and patterns).
Repeat Step 4 and 5, applying alternatively detergent and mild bleaching agent until the stain is fully gone.
Apply a stain remover gel or spray to the fabric and let it sit there for 3 to 5 minutes.
Now wash the cloth with laundry detergent. If the stain still remains, rub the detergent into the stained portion and soak the cloth in warm water for half an hour and rinse it well.