Tear open the chilies, and remove the seeds. It's okay if a few seeds remain.
Heat a large skillet over medium heat. Add the chilies, onions, and garlic and roast them, stirring frequently, until the onions are charred in places and the chiles are aromatic, about 10 minutes. Set aside.
1 medium onion, 3 cloves garlic
Meanwhile, in a separate pot, bring about 6 cups of water to a boil. Set up an ice bath by filling a large bowl with water and adding at least a cup of ice. Carefully drop the tomatoes into the boiling water and then remove with a slotted spoon after 30 seconds. Place in the ice bath.
5 medium tomatoes
Remove the tomatoes into an ice bath and peel off the skin (you may need the end of a paring knife to help you start peeling the skin away). Cut out the top of the tomatoes where the stems were and then cut the tomatoes in half.
Discard the water used for the tomatoes, and add 4 cups of water, the beef stock, and the tomato sauce. Bring to a simmer.
2 cups beef stock, 1 cup tomato sauce
Transfer the chilies, onions, garlic and tomatoes to the water/stock. Add in the oregano and cumin. Lower the heat to low/medium and simmer for about 15 minutes
Working in batches, carefully transfer the chili mixture to a blender or large food processor. Puree for about 1 minute, until very smooth.
Pass the puréed sauce through a fine colander or fine-mesh sieve into a heat-proof bowl.
Return the strained sauce to the stove and heat for about 15 minutes. Add 2½ teaspoon salt. Taste and add another ½ tsp, if desired.
2½ teaspoon Kosher salt
Use at once, or store in a container with a tight-fitting lid. Keep in the fridge for up to 1 week or freeze for up to 2 months.
Video
Notes
See the video near the top of the blog post for visual guidance. If you liked the video, please subscribe to our YouTube channel.The recipe can be easily cut in half. However, we love making the full batch and freeze what we don't use. Take extra caution when transferring any of the hot liquid and vegetables from the pot to the blender. Cover with a kitchen towel.We typically end up adding 3 full teaspoons of salt to the sauce. Taste after adding the initial 2½ and see if you think it could use a little more.