In a skillet over medium high heat, saute the onion in the olive oil until it is just beginning to brown, about 4 minutes.
2
Lower heat to medium, add the garlic and saute another minute or so.
3
Add the pureed black beans and oregano. Stir well.
4
Stir constantly over medium heat until the puree becomes a moundable paste, about 5 minutes. The bottom of the pan will become visible as you stir, and the mixture will not run back.
5
Season with cayenne or Tabasco sauce and stir another 30 seconds.
6
Serve hot or room temperature as a dip or use as a filling in quesadillas. Store in the refrigerator.