Add all ingredients to a medium saucepan and stir to combine.
Bring to a boil, then lower heat and simmer until desired thickness, about one hour
Notes
If you use fresh veggies for the sauce (vs celery seed and garlic powder) you may want to blend the cooked sauce in a blender, until smooth.
The recipe calls for a teaspoon of pepper. At this amount, you will taste the pepper. I preferred less pepper.
You can use either ketchup OR tomato sauce in this recipe. Ketchup is sweeter, so you will get a sweeter BBQ sauce unless you reduce the amount of sugar. Tomato sauce is less sweet.