Crispy Oven Beef-and-Bean Tostadas

Preheat oven to 400 degrees F (200 degrees C).

Mix garlic salt, onion powder, garlic powder, cumin, and black pepper together in a small bowl.

Heat a large skillet over medium-high heat.

Cook and stir beef, onion, and garlic in the hot skillet until browned and crumbly, 5 to 7 minutes; drain and discard grease.

Keep warm while preparing tostada shells.

Brush oil over both sides of tortillas and arrange on a baking sheet.

Bake tortillas in preheated oven until crisped on top, about 5 minutes.

Flip tortillas and continue baking until other side crisps, 2 to 3 minutes more.

Heat refried beans in a saucepan over medium-low, stirring regularly until hot, about 5 minutes (see Cook's Note).

Divide refried beans between tostadas and spread over one side of each; spoon ground beef mixture over the beans.

Top each tostada with lettuce, Cheddar cheese, and diced tomato.