Pat the beef cubes completely dry with paper towels and season generously with salt and pepper. Heat vegetable oil in a heavy-bottomed Dutch oven over medium-high heat until it shimmers. Working in batches to avoid overcrowding, sear the beef cubes on all sides until deeply golden brown, about 8-10 minutes total per batch. Transfer seared beef to a plate and set aside.

Reduce heat to medium and add diced onions to the same pot. Cook for 5-7 minutes until onions become translucent and start caramelizing. Add minced garlic and cook for another minute until fragrant. Push onions to one side of the pot and add chili powder, cumin, smoked paprika, oregano, and cayenne to the cleared space. Stir the spices for 30-45 seconds until aromatic.

Add tomato paste to the bloomed spices and cook for 2 minutes, stirring constantly until the paste darkens. Pour in beef broth gradually, scraping up all the browned bits from the bottom of the pot. Add diced tomatoes with their juices, stirring everything together until well combined.

Return the seared beef to the pot along with any accumulated juices. Bring the mixture to a gentle boil, then reduce heat to low. Cover partially, leaving the lid slightly ajar. Simmer for 2-2.5 hours, stirring occasionally, until the beef is fork-tender and the chili has thickened. In the final 15 minutes, stir in apple cider vinegar. Taste and adjust seasonings as needed.