Prepare the Beef
Season the beef chuck roast with salt and pepper.
Heat vegetable oil in a large skillet over medium-high heat. Sear the beef on all sides until browned, about 3–4 minutes per side.
Slow Cook the Beef
Transfer beef to a slow cooker. Add onion, garlic, beef broth, diced tomatoes with green chilies, cumin, chili powder, smoked paprika, salt, and pepper.
Cook on low for 8 hours or high for 4–5 hours, until the beef is tender and shreds easily with a fork.
Shred the Beef
Remove beef from the slow cooker and shred using two forks. Return shredded beef to the slow cooker and mix with the juices.
Assemble the Enchiladas
Preheat oven to 375°F (190°C).
Spread ½ cup enchilada sauce over the bottom of a 9×13-inch baking dish.
Place about ½ cup shredded beef in the center of each tortilla, sprinkle with cheese, roll tightly, and place seam-side down in the baking dish.
Top and Bake
Pour remaining enchilada sauce over the rolled tortillas and sprinkle with the rest of the cheese.
Cover with foil and bake for 20 minutes. Remove foil and bake for an additional 10 minutes, until cheese is melted and bubbly.
Serve
Garnish with fresh cilantro and serve with sour cream if desired.