Misu Tomato Sauce

1 teaspoon cooking oil
1/2 cup finely minced ripe tomatoes
1/2 teaspoon freshly ground pepper
1 teaspoon finely minced garlic
2 tablespoons misu (salted bean paste, available in Oriental stores)
1/2 cup chopped onion
1/2 teaspoon apple cider vinegar

In a small skillet, heat oil and saute garlic until light brown, then onion until transparent and tomatoes until soft. Add bean paste. Mix and mash the whole mixture with a fork. Add vinegar and pepper. Bring to a boil. Serve with boiled fish.