When oil is heated, add the onion and saute until translucent but not brown, approximately 5 minutes. Add the garlic and cook until fragrant, approximately 30 seconds.
Add the cumin, chipotle powder, chile powder, pinch of salt and sugar. Stir to combine and toast the seeds until they are fragrant to open them up, approximately 1-2 minutes.
Add the tomato sauce and 1/2 cup water. Stir to combine. Reduce heat to low and let the sauce simmer for at least 15 minutes. The longer the better, so if you can start this earlier than the flavors will continue to develop and make a more robust tasting sauce.
Add additional water as necessary as sauce continues to cook. Use in your favorite enchilada or Mexican recipe.
Notes
The heat for this recipe is moderate. For a mild heat, use 1/2 tablespoon of the chipotle and chili powders each. For a spicy sauce, use 1.5 tablespoons of the chipotle and chili powders each.
Keep in mind that the exact powders that you use can vary greatly in heat level. It is best to start off with less chili powder and add more as you need to than to end up with a sauce that is too hot!
The longer you can let this sauce cook, the better it will taste.
If you cannot find chipotle powder, I would recommend using the same measurement of chipotle in adobo sauce. You could even finely grind or chop up the peppers themselves as well and throw them in.
You can skip the sugar, but it helps round out the acidic and sharp flavors that can come with tomatoes.