1. In a large skillet over medium-high heat, brown ground beef. Add farro, tomato sauce, water, cider vinegar, cumin, smoked paprika, cayenne, chili powder, and oregano. Simmer until thick, about 5 minutes, then season with salt and pepper. Serve in taco shells topped with shredded cheddar cheese, lettuce, diced tomatoes, onions (if desired), and sour cream.