Step 1

Preheat oven to 450°F. Coat 2 baking sheets with cooking spray.

Step 2

Heat a large nonstick skillet over medium-high heat. Add beef and 1/2 cup onion; cook, stirring and breaking up beef with a wooden spoon, until beef is browned, about 6 minutes. Remove from heat; stir in ketchup.

Step 3

Arrange tortillas on prepared baking sheets. Divide beef mixture over tortillas in an even layer; sprinkle each with 3 tablespoons cheese. Bake until bottoms of tortillas are crisp and cheese is melted, about 5 to 7 minutes.

Step 4

To serve, sprinkle each pizza with a tablespoon remaining onion, 1 tablespoon pickles, 1/4 cup tomato and 1/4 cup lettuce. Cut each pizza into 4 wedges to serve. Yields 1 pizza (4 wedges) per serving.