Gather all ingredients and equipment.
Thinly slice the red onion (about 1/4 inch thick) in half moons and place in a small container. Sprinkle the onions with the sugar and salt and coat evenly.
Place the vinegars and spices in a microwave-safe container. Heat for about 1 minute or until completely warm.
Pour the warm vinegars and spices over the red onions and wrap the plastic wrap two times. The first time place the plastic wrap directly on top of the onions and liquid. The second time wrap the plastic wrap around the container.
Allow to sit for 4-6 hours. The longer the better the flavor!