Prep/slice/ chop all ingredients, separating those for salad and those for vinaigrette.
Place sliced red onions in a small bowl. Add the warm water with a dash of salt and 1 TBSP lime juice. Let soak for about 10 minutes.
After 10 minutes, drain the onion slices.
In a salad bowl, combine arugula, mango, avocado and macerated red onion slices.
To make your vinaigrette, combine all the ingredients in a small jar/bottle. Cover and shake until the ingredients are well mixed.
Dress salad and serve immediately.
