CopyKat.com is the creation of Stephanie Manley. Stephanie started publishing recipes on the web in 1995 as a means to capture her family recipes in a format that they would not be thrown away.
Over the years 
This is the style of barbeque sauce that I grew up with, this is a two step basting process. First you baste the meat with a flavorful basting sauce, and when the meat is almost done, then you add the real barbeque sauce. Recipe comes from Sue A. Mertens Minick from Hazelwood, MO. She actually found this site on the internet! And yes, she is family 
Missouri Style Barbeque Sauce
Basting Sauce
1 C. White Vinegar
2 C. Water
2 Tbsp. Worcestershire Sauce
1 tsp. Red Pepper
1/2 C. Butter
Cook until mixed. Use as a baking sauce for chicken or pork steak until nearly cooked. Then use the finishing sauce for the last part of the cooking.
Finishing Sauce
1 1/2 C. Butter
1 Tbsp. Tabasco Sauce
2/3 C. Worcestershire Sauce
2 C. Catsup
2/3 C. White Vinegar
1 large onion, diced
1 tsp. Salt
1/2 tsp. Pepper
1 Garlic Bud, chopped
2 tsp. chili powder
Combine all ingredients and cool until slightly thick. Use during the last part of cooking the meat.
In the description of the recipe, you said that the first baste is with an onion flavored sauce. There is nothing onion flavored in the baste recipe. Is there an ingredient missing??
Sue is actually family to me, I was thinking of other family members that add onions to this initial basting sauce, hence my write up that way. So if you like onion, I would suggest you add some and give the basting sauce a slightly different flavor.