Sauté aromatics. Heat a large skillet over medium heat. Add olive oil if using. Cook onion 3 to 4 minutes until softened. Add garlic and cook 30 seconds.
Brown the beef. Add ground beef and cook 5 to 6 minutes, breaking it up, until browned. Drain excess fat if needed.
Build flavor. Stir in tomato paste and cook 1 minute. Add chili powder, cumin, paprika, oregano, salt, pepper, and optional cayenne. Stir 30 seconds to bloom the spices.
Simmer. Add tomato sauce and broth. Simmer 3 to 5 minutes until saucy and thickened. Taste and adjust salt/spice. Stir in lime juice if using.
Warm tortillas. Warm tortillas in a dry skillet or microwave wrapped in a damp towel.
Assemble. Fill tortillas with beef and add toppings. Serve right away.