01 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook for 2 to 3 minutes until softened.
02 - Stir in minced garlic and cook for 30 seconds until fragrant.
03 - Add ground beef and break it up with a spoon. Cook until browned, about 5 to 7 minutes.
04 - Mix in ground cumin, chili powder, smoked paprika, dried oregano, salt, and black pepper. Stir and cook for 1 minute.
05 - Incorporate tomato paste, mix thoroughly, then pour in beef broth or water. Simmer for 3 to 4 minutes until the mixture thickens. Remove from heat.
06 - Combine diced tomatoes, red onion, minced jalapeño, chopped cilantro, lime juice, and salt in a bowl. Toss well to combine.
07 - Preheat oven to 375°F. Place corn tostada shells on a baking sheet and sprinkle half of the cheese over them. Bake for 3 to 4 minutes until the cheese melts.
08 - Top each baked shell with a spoonful of beef mixture, salsa, remaining cheese, avocado slices, and a dollop of sour cream. Garnish with fresh cilantro and serve with lime wedges.