Place a pizza stone or heavy baking sheet in oven. Preheat oven to 450°.
While oven preheats, heat a large nonstick skillet over medium-high heat. Add beef, onion, and salt to pan; cook 3 minutes or until beef is browned. Remove pan from heat.
Combine mayonnaise and ketchup in a small bowl, stirring with a whisk. Spread mayonnaise mixture over crust, leaving a 1/2-inch border. Spread beef mixture evenly over mayonnaise mixture. Sprinkle cheeses over beef. Top evenly with tomato slices and pickles; sprinkle evenly with pepper. Bake at 450° for 8 to 10 minutes or until cheese is lightly browned. Cut pizza into 8 wedges.