Preheat oven to 400˚F. Wrap the beets individually in aluminum foil. Place on a rimmed baking sheet and roast until tender when pierced with a knife, about 1 hour. Allow to cool.

Using a sharp paring knife, remove the peel and white pith from the blood oranges and navel oranges and discard. Over a medium bowl, slice between the membranes of two of the blood oranges to remove the segments and place in the bowl. Squeeze the juice from the membranes into the bowl, and discard the membranes. Slice the remaining blood orange and navel orange crosswise into thin rounds and add them to the bowl. Stir int he lemon and lime juices. 

Peel the beets and slice into thin rounds. Arrange on a serving platter, then top with citrus mixture, including the juice. Layer the fennel and onion on top, then drizzle generously with oil. Season to taste with salt and pepper, and allow to rest for 5 minutes to let the flavors develop. Serve garnished with cilantro.