Heat a cast-iron skillet (my southern preference) to a medium high heat, place a pat of butter (roughly 1 Tablespoon) in the skillet and melt
Sear the roast in the skillet with the butter - place in the slow cooker
In a medium measuring bowl/cup combine the cayenne/chipotle pepper powder, comino, paprika, garlic cloves, vegetable broth, tomato paste, jalapeƱos, onions, and lime juice - whisk together and pour over the roast in the slow cooker
Cook on low for 6 to 8 hours or high for 3 to 4 hours
When the roast is done, shred with a couple of forks and let the shredded beef sit in the juices in the slow cooker on warm for an additional 30 minutes to 2 hours
*Tacos
Serve in corn or flour tortillas topped with your favorite taco toppings - avocados, tomatoes, cilantro, diced jalapenos, salsa, sour cream, avocado cream....