First, heat a pan on medium high heat. When its heated, cook onions in oil until they are carmalized (light to dark brown). If they turn black, don't worry, they'll still taste ok.
Once you get that going, put the cans of tomato paste in a small pot. Add molasses and apple cider vinegar. (A LITTLE , or rather large, HINT: Molasses makes a BBQ sauce sweet. Apple cider vinegar makes BBQ sauce tangy. SO, depending on how you like your BBQ sauce- for example, I prefer mine a little more sweet and tangy than some people, you might want to add more or less of both depending on taste.) Stir this for a while, and your onions should be done. Stir onions in along with all your other spices.
A NOTE ON SEASONING: BBQ sauce absorbs a lot of flavor, and the mixture of tomato past, molasses and apple cider vinegar are pretty overpowering. To compensate, add a lot of spices. It might seem like you're adding too much, but you're not. Add some more. And for the best results until you get it down, taste periodically.
Liquid Smoke: THIS IS NECESSARY. otherwise, your BBQ sauce will taste like wierd katchup. Add a good amount depending on how smokey you want your BBQ sauce to be. You can also use more of this in place of salt.
Salt: use a lot of it and if you screw up and make it too tangy or sweet the salt will cover it up. Garlic Powder: use a good amount of this. Usually how I judge it is I add until I think I added too much, then i put more in (the same applies for salt, actually). Ground Red Pepper: if you like spicy BBQ add a good amount of it, but if you don't it tastes fine without it, though I might call you a wimp.
Spike: I always use this stuff. If you don't have spike, you're not a vegan cook. With that said, use a good amount of this, too.
Pepper: duh. to taste.
Whatever else: See, one of the coolest things about BBQ sauce is that it can have a million different tastes. KC Masterpiece won't cut it and all of the good sauces have honey BBQ sauce Experiment, make your own, and have fun.
Soundtrack: Youth of Today: Were Not In This Alone LP