In a saucepan, add the dry ingredients: salt, sugar, chili powder, paprika, black pepper, garlic salt, onion powder, and light brown sugar. Mix well to break up any lumps. Add ketchup, melted butter, water, vinegar, and Worcestershire sauce. Bring sauce to a simmer over low heat. Continue to simmer, stirring the entire time until the sauce has reduced and thickened, about 15 minutes. (Keeping the heat low helps prevent the butter from separating and the sugar from burning.)
Sauce is done when it thinly coats a spoon and has reduced by about ⅓. Cool to room temperature, stirring occasionally so it doesn’t stick to the bottom. Store in a covered container in the refrigerator (keeps for months, thanks to the vinegar). Makes about 3 cups.