01 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook until softened, about 2 to 3 minutes.
02 - Stir in minced garlic and cook for 30 seconds until fragrant.
03 - Add ground beef and cook, breaking it apart with a spoon, until fully browned, approximately 5 to 7 minutes.
04 - Mix in ground cumin, chili powder, smoked paprika, oregano, salt, and black pepper. Cook for 1 minute to release aromas.
05 - Incorporate tomato paste, stirring to combine. Pour in beef broth or water and simmer for 3 to 4 minutes until sauce thickens. Remove from heat.
06 - In a bowl, combine diced tomatoes, red onion, jalapeño, cilantro, lime juice, and salt. Toss gently to mix.
07 - Preheat oven to 375°F. Arrange tostada shells on a baking sheet, sprinkle with half of the cheese, and bake for 3 to 4 minutes until cheese melts.
08 - Top each tostada with beef mixture, fresh salsa, remaining cheese, avocado slices, and a dollop of sour cream. Garnish with cilantro and serve with lime wedges.