Prep the fruit. Remove the top and bottom of the pineapple. Slice in half and remove the core. Dice into ¼" pieces. Slice the mango from the core and remove the skin. Dice into ¼" pieces.
Prep the veggies. Dice the red onion into small pieces and set aside. Remove the top of the jalapeño and slice in half. Remove the seeds and ribbing and mince into small pieces. If you want a spicier salsa, mince the whole jalapeño. Chop the cilantro leaves finely.
Combine ingredients.In a medium bowl, mix together the pineapple, mango, red onion, cilantro. Season with salt and pour the lime juice over the ingredients. Mix again until all the ingredients are well distributed. Store in an airtight container for up to 3 days in the refrigerator.