Preheat oven to 325°. In a small bowl, combine chili powder, cumin, 3 ½ teaspoons salt, and 1 teaspoon pepper. Cut roast into 4 pieces; season all over with spice mix.

In a large Dutch oven over medium-high heat, heat oil. Working in batches if needed, sear beef on all sides until a deep brown crust forms, 1 to 2 minutes per side. Transfer beef to a large plate.

Reduce heat to medium and add scallions and garlic to pot; season with ½ teaspoon salt. Cook, stirring occasionally, until fragrant, about 2 minutes. Add tomato paste and chile sauce and cook, stirring frequently, until warmed through, about 2 minutes. Stir in orange juice and scrape any browned bits from bottom of pot. Stir in broth, cilantro, and oregano and return beef to pot. Increase heat to high and bring to a simmer.

Partially cover with a lid and transfer pot to oven. Roast 3 hours. Uncover and continue to roast until meat easily shreds with a fork, about 1 hour more.

Shred meat in pot with 2 forks; season with salt. Top with cilantro and serve with lime wedges alongside.

In a small bowl, combine chili powder, cumin, 3 ½ teaspoons salt, and 1 teaspoon pepper. Cut roast into 4 pieces; season all over with spice mix.

In a large slow cooker, combine scallions and garlic. Place beef on top.

In a large measuring cup or bowl with a pouring spout, whisk tomato paste, adobo sauce, orange juice, and broth. Pour over beef. Add cilantro and oregano. Cover with lid and cook on low 8 hours, or until beef is tender enough to shred with a fork.

Shred meat in slow cooker with 2 forks; season with salt. Top with cilantro and serve with lime wedges alongside.