Cut the fillets in half lengthwise, then slice each half crosswise into thin strips and place in a medium-size nonreactive bowl. Add the orange, lemon, and lime supremes and the orange, lemon
, and lime
juices and stir to combine. Add the onion
, avocado, and chile, and gently fold to combine.
Refrigerate the mixture for 1 hour for well-done fish or serve immediately for fresh tartare, sushi-like texture.
Serve cold in small bowls, with tostones
, if using, if desired.