Cut onions into quarters, trim both the ends and peel off papery outer layer. Separate the onion layers and punch out stars using a star cookie cutter. Cut out about 3 cups of stars. Reserve left-over onion scraps to use in another recipe or freeze.
In a small saucepan, add water, vinegar, sugar, salt and red pepper flakes and bring to a boil. Boil for 5 minutes.
Clean a 1 quart mason jar, lid and ring and set aside. Add onion stars and fill the mason jar with boiling liquid. Place lid and ring over filled jar and hand tighten.
Let cool to room temperature and then place them in the refrigerator and allow onions to pickle for 2-3 days and Enjoy! Note: These onions are quick pickled and not canned, so they must be stored in the fridge. Can be stored in the refrigerator for about 10 days.