01 - Heat the vegetable oil in a large skillet over medium heat. Add the chopped onion and sauté for 2–3 minutes until softened.
02 - Add the minced garlic and cook for 30 seconds until fragrant.
03 - Add the ground beef, breaking it up with a spoon. Cook for 5–6 minutes until browned and cooked through. Drain excess fat if necessary.
04 - Stir in the cumin, chili powder, smoked paprika, oregano, salt, and pepper. Mix well and cook for 1 more minute.
05 - Add the refried beans to the skillet and mix thoroughly with the beef. Cook for 2–3 minutes, stirring often, until heated through. Remove from heat.
06 - Preheat the oven to 350°F. Arrange the tostada shells on a baking sheet and warm for 3–4 minutes, or until crisp.
07 - Spread a generous layer of the beef and bean mixture on each tostada shell.
08 - Top with shredded lettuce, diced tomatoes, cheese, sour cream, olives, cilantro, and a squeeze of lime. Add hot sauce if desired.
09 - Serve immediately while the tostadas are crisp.