Pickle the onions by combining the thinly sliced red onion and 1-2 tablespoon of red wine vinegar in a small bowl. Cover and chill for an hour or so. Drain onions and discard any vinegar remaining in the bowl.
Assemble Mango Salad
In a medium serving bowl, whisk together one tablespoon red wine vinegar and lime juice. Slowly whisk in oil.
Put the cut mangoes, avocado, cucumber and red onion in the bowl with the dressing. Toss gently to coat. Salt and pepper to taste. Serve immediately.
Notes
Pickling the onions is an optional step; however, we really like what it does for the flavor of the onions. If you forget or don’t have time, don’t worry. In that case, just throw the onions in with the fruit and cukes.