Pickled Red Onions

Directions:

1. Add sliced onions to a container with a tight lid, such as a mason jar.
2. Add the next 4 ingredients to a small pot over medium high heat. Bring to a boil, making sure that the salt and sugar dissolve completely.
3. Remove from heat, and pour over onions. Add crushed red pepper flakes to mixture, if desired.
4. Allow onion mixture to cool to room temperature; cover with lid and refrigerate for at least 2 hours before using.