2 Hass avocados, peeled and cut into 1/2 -inch wedges
Using a sharp stainless steel knife, peel the grapefruits and oranges; be sure to remove all of the bitter white pith. Cut each fruit crosswise into five 1/4-inch slices. Squeeze enough of the remaining citrus to yield 1/3 cup of juice; set aside.
Using a citrus reamer, squeeze one half of the pomegranate until you have 2 tablespoons of juice. Remove and reserve 1/4 cup of seeds from the other half.
In a bowl, whisk the citrus and pomegranate juices with the orange-flower water and oil. Season with salt and pepper.
In a large bowl, toss the watercress with 1/4 cup of the dressing and half of the Pickled Red Onions. Arrange the watercress on plates. Add the avocados to the bowl and gently toss with 3 tablespoons of the dressing. Arrange the avocado and sliced oranges and grapefruit on the watercress; drizzle with the remaining dressing. Garnish with the remaining Pickled Red Onions and the pomegranate seeds and serve.