Bring a skillet to medium heat and then toast the dried guajillo and dried ancho peppers for 6 minutes, flipping once. Remove the skillet from the burner and reserve the peppers.
Increase the burner heat to medium-high and add the peppers and garlic to a medium sauce pan. Cover with water and bring to a boil. Reduce the heat to medium and simmer for 15 minutes until the peppers have rehydrated.
While the peppers rehydrate, cut the beef roast into four or five chunks and trim off most of the fat. Then rub the beef heavily with salt and pepper, all over. Heat a Dutch oven over high heat. Add 3 tablespoons of oilive oil and sear the chuck roast pieces on all sides (about 10 minutes). Remove from the Dutch oven and reserve.
In a blender (Vitamix) add the rehydrated peppers and garlic, cumin, Sukrin Gold, vinegar, oregano, and 1/2 cup of rehydrated water from saucepan. Blend until smooth. Add more water, as needed.
Place the seared chuck roast pieces in a slow cooker. Pour sauce from the blender over the meat and turn on high for 6 hours. (If you prefer, you can use low setting for 8 hours.
When done, shred with two forks, drizzle lime juice on plated meat, and serve in Keto Almond Flour Tortillas, or on a plate with chopped red onion, cilantro, radish, diced tomatoes, or red cabbage.
You can also skip the slow cooker and roast the beef in a 275 degree oven for 5 hours.
For a smoky flavor add one chipotle in adobo sauce to the blender.