My experience at RT, is that each place does it's own thing, but they all are LOADED with various chili powders in a tomatoe paste base, non-diluted.
I suggest starting with, a Spanish blend chili powder, a small amount sugar and only a touch of onion and garlic "powder" and a bit of salt if needed.
For heat I suggest using hungarian hot paprika and/or cayenne
If the spanish blend dosen't contain Cumin, I suggest adding a bit, but most chili blends have cumin.
Too much chili powder will produce bitter results, especially with the already bitter tomato paste. The sugar will help counteract this.
I dont measure when using chili powders, since they tend to† lose potency with storeage, and flavor and heat varies by brand. I make this type of sauce mostly by taste.
Hope this helps