Crisp watermelon and creamy avocado combine to make an unusual and appealing salad.
In a small bowl, combine onion and vinegar. Marinate, covered, in refrigerator for several hours or overnight.
Cut avocados in half; remove pits and skin. Cut into 1-inch chunks and toss with the lime juice. Remove seeds from watermelon and cut into 1 1/2-inch chunks.
Toss together watermelon, avocado, orange juice, olive oil, and cilantro sprigs, reserving some sprigs for garnish. Drain onion and add to salad; add salt and pepper to taste. Toss again and garnish with reserved cilantro.