Cut the onion into thin half rings, chop the olives in half, and cut the cucumbers into thin strips.
Use a spoon to scoop out the pulp from the grapefruit.
Make the dressing: In a bowl, combine lemon juice, salt and red pepper.
In another bowl, mix the onion, cucumbers, olives, and grapefruit pulp. Add the dressing and mix. The salad is ready.