Slice 2 red onions very thin. Here's a refresher on How to Cut an Onion. Add them to a medium bowl.
Sprinkle 2 teaspoons of salt on the onions. Add freshly cracked black pepper. to taste. (I like to add a lot! At least 1/2 teaspoon)
Squeeze the juice from 3 lemons (or limes!) over the onions.
Stir and let sit for at least 5 minutes. I prefer to let my onions pickle for at least 30 minutes. They are even better (and pinker) after 2-3 hours. Be sure to stir them occasionally so all the pickle love can be distributed!