Place the corn, jalapeno(s), tomato, cilantro, and red onion in a bowl. Squeeze the lime juice over the top, then sprinkle with the salt and pepper. Give everything a giant stir until it is evenly incorporated. Stir in the feta (if using).
Taste and adjust the seasoning as you wish—if it seems bland, add a little salt; add lime if you want it more zingy; if you want it spicier, add more jalapeno (or some of the membranes and seeds). If time allows, refrigerate for 15 minutes to allow the flavors to marry. Enjoy with corn chips, add it to a salad, or spoon over grilled chicken or fish.
Notes
TO STORE: Transfer leftover corn salsa to an airtight container and refrigerate for 3 to 4 days. (The storage life will depend on the freshness of the ingredients when you first make the salsa.)