Begin by heating your vegetable oil (or the butter and olive oil mixture) in a large skillet over medium heat. Once hot, add the diced onion and sauté until it becomes translucent, about 5 minutes.
Next, stir in the minced garlic and diced carrots. Sauté for an additional 3-4 minutes until the garlic is fragrant and the carrots begin to soften.
Sprinkle the all-purpose flour over the sautéed vegetables and stir continuously for about 1 minute.
Add the chili powder, Mexican oregano, and ground cumin to the skillet. Stir well to combine, allowing the spices to toast for about 1 minute.
Pour in the 2 1/2 cups of water, stirring to combine all the ingredients. Bring the mixture to a gentle simmer. Allow it to cook for about 10-15 minutes, stirring occasionally.
After simmering, taste your sauce. Add salt as needed to enhance the flavors.
Your Red Enchilada Sauce is now ready to use! Pour it over your favorite dishes or store it for later.
