For the fruit salad, peel and slice the avocado. Sprinkle it with 1 tablespoon of lime juice. Peel, seed and slice the papaya thinly. Sprinkle with the remaining lime juice. Peel the oranges and grapefruit. Cut the fruit into segments. Slice the red onion.
In a large bowl, combine the avocado, papaya, orange and grapefruit segments and onion. Set aside. If you are using pomegranate, scoop out seeds and set them aside in a small bowl.
For the dressing whisk together the orange juice, lime juice, honey, pepper flakes and oil.
To serve, pour the dressing over the fruit and toss well. Spoon onto a lettuce-lined platter or large bowl. Sprinkle the pomegranate seeds over it all.