01 - Heat a large skillet over medium heat. Add ground beef and cook, breaking it up with a spoon, until browned, approximately 5 to 6 minutes. Drain excess fat if necessary.
02 - Add chopped onion and minced garlic to the skillet and sauté for 2 to 3 minutes until softened and fragrant.
03 - Stir in chili powder, ground cumin, smoked paprika, dried oregano, salt, and black pepper. Cook for 1 minute until the spices release their aromas.
04 - Add tomato sauce and simmer for 3 to 4 minutes, stirring occasionally, until the mixture thickens slightly. Remove from heat and keep warm.
05 - In a small saucepan over medium heat, warm the refried beans until heated through, stirring occasionally. Add a splash of water or broth if the consistency is too thick.
06 - If desired, quickly warm the tostada shells in a large skillet with a small amount of vegetable oil for enhanced crispness, approximately 30 seconds per side.
07 - Spread a generous layer of refried beans on each tostada shell. Layer with seasoned beef, shredded lettuce, cheese, diced tomato, and desired toppings including sour cream, radishes, cilantro, and jalapeño slices.
08 - Arrange assembled tostadas on plates and serve immediately with lime wedges on the side.