In a medium saucepan, heat 2 tablespoons of the olive oil over medium heat.
Add the diced onions and saute 3 minutes.
Add the garlic and cook 2 minutes longer or until garlic is fragrant and onions are translucent.
Whisking constantly, add the arrowroot flour, chili powder, cumin, salt, cayenne (if using), and remaining 2 tablespoons oil.
Add the tomatoes and cook for a few minutes to blend the flavors together.
Add the water a little at a time, making sure to stir. If the sauce seems too runny, stop adding water. If it seems too thick, add more.
Simmer the sauce on low heat for 10 minutes.
Put all ingredients in a blender or use an immersion blender and blend to desired consistency.
Season with additional salt if necessary.
Notes
If you accidentally added a little too much water, just simmer the sauce a little longer until it reaches the desired consistency.This enchilada sauce is great to have already made for when you need it for a quick meal.Try making a double batch and freezing it so you always have it ready!