In a skillet over medium heat, cook the ground beef and diced onions until browned. Drain excess fat.
Stir in mustard, ketchup, garlic powder, onion powder, salt, and pepper. Cook for another 2 minutes.
Lay out a whole wheat tortilla, place a tostada shell in the center, and add a portion of the beef mixture.
Top with shredded lettuce, tomatoes, and cheese.
Fold the tortilla edges over the center, sealing it into a wrap.
Lightly coat a pan with cooking spray and cook the wrap seam-side down until crispy, then flip and cook the other side.
Serve warm and enjoy!