Cebollas Encurtidas Para Panuchos

From Diana Kennedy's book "The Essential Cuisines of Mexico."

2 Medium white onions, finely sliced into rings, about 3 cups

4 cups boiling water

1/2 cup seville orange juice

1/2 cup of water

1 scant tablespoon dried mexican oregano

1 Habanero chile, finely sliced

salt to taste

Immerse the onion rings in a sauce pan of boiling water for a few seconds until slightly blanched. Drain well and put into a nonreactive bowl. Mix in the rest of the ingredients, and set aside to season for at least 2 hours before using.