In a small bowl, mix chili powder, cumin, smoked paprika, garlic powder, onion powder, cayenne (if using), and salt. Set aside. 2. Heat a large skillet over medium-high heat. Add ground beef and cook, breaking it apart with a wooden spoon, until browned and no longer pink, about 5-6 minutes. 3. Drain excess fat, leaving about 1 tablespoon in the skillet. 4. Reduce heat to medium. Add the spice mixture and stir for 30 seconds until fragrant. 5. Pour in 1/4 cup water and stir, scraping up any browned bits. Simmer until liquid mostly evaporates, about 2 minutes. 6. While beef cooks, prepare cold brew: combine coarsely ground coffee and cold water in a jar or French press. Stir gently, cover, and let steep at room temperature for 12-24 hours (or use hot steep method: steep in hot water for 4 minutes, then strain over ice). 7. Strain cold brew through a fine-mesh strainer (or press plunger). Fill a glass with ice, pour cold brew over, and add a splash of milk or cream if desired. 8. Warm tortillas in a dry skillet or microwave. Fill each with seasoned beef, then top with lettuce, tomato, cheese, sour cream, cilantro, and a squeeze of lime. Serve immediately with iced coffee.