Heat two teaspoons of the oil in a skillet over medium heat. Place the tortillas in the hot skillet, pressing them flat, and cook for 3-4 minutes on each side, or until golden brown and crisp.
Heat the last 2 teaspoons of oil in a skillet over medium heat. Add the onion and cook, stirring often, for 2-3 minutes.
Add the ground beef, making sure to break it up into crumbles with the spatula, as it cooks.
Add the chili powder, cumin, paprika, garlic powder, coriander, and oregano to the beef along with sea salt and freshly cracked pepper, to taste. Cook until cooked through, about 6-7 minutes.
Add the garlic and cook, stirring constantly, for 1 minute.
Remove from heat. Add 1/4 cup fresh cilantro; mix well.
Place the crisp tostada shells on a plate then spread some of the meat and bean mixture on top. Add shredded cheese, shredded lettuce, sour cream, tomatoes, and cilantro.
Serve with salsa and lime wedges on the side. Enjoy.