Heat the oil in a large saucepan over medium heat. Add the onion, garlic, and red pepper. Sauté until fragrant, about 3 minutes. Add the ground beef and brown, about 5 minutes. Stir in the tomato paste, chili powder, cumin, black pepper, cinnamon, and salt. Simmer, stirring occasionally, until the sauce has thickened slightly, about 12 minutes. Spoon onto the buns, sprinkle with the Cheddar, and top each sandwich with a dollop of the sour cream.
Tip: If you have any leftover filling, use it for tacos the next day. Scoop the meat into a shell and add salsa.