Soak 1/4 thinly sliced red onion in cold water, about 10 minutes. Whisk 1/4 cup orange juice, the juice of 1 lime, 1 tablespoon honey, 2 teaspoons dijon mustard, 1/2 teaspoon salt, and pepper to taste in a bowl. Whisk in 3 tablespoons olive oil. Drain the onion; toss with 2 bunches watercress, 2 sliced avocados, 2 segmented oranges and the dressing. Top with chopped toasted hazelnuts.