Soak thinly sliced red onion in cold water, 10 minutes; drain.
Combine sour cream, lime juice and hot sauce in a bowl.
Arrange thinly sliced avocados on a platter.
Top with thinly sliced radishes and the onion.
Drizzle with the sour cream dressing and sprinkle with chopped cilantro and crumbled feta cheese.
*This recipe brought to you by Food Network Magazine.*