01 - Heat a large skillet over medium heat. Add ground beef and cook, breaking up with a spatula, until browned and mostly cooked through, about 5 to 6 minutes.
02 - Add finely chopped onion to the skillet and cook for 2 to 3 minutes until softened. Stir in minced garlic and cook for 30 seconds.
03 - Sprinkle in ground cumin, chili powder, smoked paprika, dried oregano, salt, and black pepper. Stir thoroughly to coat the meat evenly.
04 - Incorporate tomato paste and beef broth or water. Mix well and simmer for 3 to 4 minutes until thickened and flavorful. Remove from heat.
05 - Heat refried beans in a small saucepan over low heat, stirring occasionally until warm.
06 - Preheat oven to 350°F (175°C). Place tostada shells on a baking sheet and bake for 3 to 4 minutes if a crispier texture is desired.
07 - Spread warm refried beans onto each tostada shell. Top with a generous portion of seasoned beef.
08 - Layer shredded lettuce, diced tomatoes, shredded cheese, sour cream, sliced jalapeños if using, and chopped cilantro atop the beef. Serve immediately with lime wedges.