01 - Bring a pot of water to a boil in a saucepan. Add tomatillos and jalapeño; simmer for 5 minutes until tomatillos turn pale green and soften. Drain and cool slightly. In a blender, combine tomatillos, jalapeño, garlic, cilantro, lime juice, and salt. Blend until smooth. Stir in chopped red onion. Chill until ready to use.
02 - Heat olive oil in a large skillet over medium-high heat. Add onion and sauté for 2-3 minutes until softened. Add garlic and cook for 30 seconds. Add ground beef and cook, breaking up with a spoon, until browned (about 5 minutes). Stir in smoked paprika, cumin, chili powder, oregano, cayenne, salt, and pepper. Cook for 1 minute. Add tomato paste and water. Stir to coat the beef and simmer for 3-4 minutes until thickened. Taste and adjust seasoning.
03 - Fill each warm tortilla with spicy beef. Top with salsa verde, crumbled cheese (if using), avocado slices, and fresh cilantro. Serve with lime wedges.