This is an easy, healthy salad that hinges on the young paddles of the prickly pear cactus. If you don't gather them yourself, you can buy them already de-spined, and sometimes already diced, in Latin Markets. One note on this salad: Eat it straight away. It will get a bit slimy if you leave it for a day or two.
Dice the nopales and toss with salt. You want all the cut sides of the nopales to have salt on them. Put them in a colander in the sink and let this drain for 1 hour. When the time has elapsed, rinse the nopales under cold water until they are no longer slimy, which should take maybe 3 to 5 minutes. Pat dry with a kitchen towel put into a large bowl.
While the nopales are sitting in the colander, mix the diced onion with a little salt and the lime juice and let them pickle a bit. This takes the harsh edge off the raw onion. If you want, you can add the minced chiles to the lime juice, too.
When you're ready, mix all the ingredients together and serve.