Sauté onion in butter until translucent. Add in minced garlic and sauté another minutes. Add in remaining ingredients and bring to a boil. Continue cooking with a low boil for 10 minutes, stirring occasionally.

Reduce heat to a simmer and continue cooking 35 - 40 minutes until mixture has thickened and is reduced by almost half. Allow to cool slightly.

Blend mixture until smooth. Cool completely. Store in air tight jar in refrigerator for up to two weeks.

Yield: about 3 cups