01 - Heat olive oil in a large skillet over medium heat. Add chopped onion and cook for 2 to 3 minutes until softened.
02 - Add minced garlic to the skillet and cook for an additional 30 seconds, stirring constantly.
03 - Add ground beef and cook while breaking it up with a spoon until browned and fully cooked, approximately 6 to 8 minutes. Drain excess fat if necessary.
04 - Stir in chili powder, cumin, smoked paprika, oregano, salt, and black pepper. Cook for 1 to 2 minutes until fragrant. Remove from heat and set aside.
05 - In a small saucepan, heat refried beans over low heat, stirring in water as needed to achieve a creamy consistency. Keep warm.
06 - Preheat oven to 350°F. Heat store-bought tostada shells on a baking sheet for 3 to 5 minutes until heated through and extra crispy.
07 - Spread a layer of warm refried beans onto each tostada shell. Top with seasoned beef, shredded lettuce, diced tomatoes, cheese, sour cream, avocado slices, and fresh cilantro.
08 - Serve immediately with lime wedges on the side.