2 tablespoons olive oil, divided
2 pounds boneless beef chuck roast
2 teaspoons chili powder
1 teaspoon cumin
1/2 teaspoon paprika
1 cup beef stock
2 tablespoons tomato paste
1 chipotle pepper in adobo sauce, minced
1 small white onion, diced
5 garlic cloves, minced
optional toppings: shredded cheese, fresh cilantro, guacamole, pico de gallo or salsa
Whisk together the chili powder, cumin, and paprika in a small bowl. Rub the spice mixture into the beef covering each side evenly. Heat 1 tablespoon olive oil in a large skillet over medium high. Carefully place the beef in the skillet and sear on each side until browned, about 2 minutes per side. Remove beef from skillet and place in the bottom of a slow cooker.
Add the remaining tablespoon of olive oil to the saute pan along with the diced onion. Saute for 3 minutes, stirring occasionally. Add the garlic and saute for 1 minute. Add the beef stock and stir the pan to deglaze it, scraping up any browned bits at the bottom of the pan with a wooden spoon. Add tomato paste and chipotle and whisk to combine. Bring the sauce to a boil, reduce heat, and simmer for 3-5 minutes until the sauce has reduced and thickened slightly. Pour the pan sauce over the beef into the slow cooker. Cook on low for 6-9 hours or on high for 3-4 hours until the beef shreds easily.
Shred the beef with 2 forks and serve in flour tortillas with desired toppings.