This recipe was originally part of a recipe for barbequed spare ribs from the Better Homes and Gardens New Cook Book (published around 1962). I've altered it to make it a bit sweeter and less acidic. I have also reduced the oil so it sticks to food better.
2 cups chopped onions
2 tablespoons vegetable oil
12 ounces tomato paste
1 cup water
1 cup dark brown sugar
1/2 cup lemon juice
1/4 cup + 2 tablespoons Worcestershire sauce (3/8ths of a cup)
1/4 cup prepared mustard (I use regular old yellow mustard)
1 tablespoon + 1 teaspoon salt
1/2 teaspoon black pepper
Note: For a darker colored sauce use a cast iron pan.
In a large frying pan or heavy saucepan, saute onions in oil until golden. Add the remaining ingredients and mix well. Simmer for 15 minutes to thicken.