Preheat oven broiler to 500 degrees.
Begin preheating oven safe sauce pan or cast iron pan with olive oil over medium-high to high heat.
Meanwhile, slice zucchini in thicker slices, ½ inch or so.
Sprinkle both sides of zucchini with garlic salt and pepper, to taste.
Once cast iron pan and oil is hot, place zucchini in pan. You want it to sizzle as you place them. If it doesn’t, the oil isn’t hot enough.
Sear zucchini for 90 seconds.
Flip and top with diced tomatoes, sliced basil, and mozzarella, in that order.
Once topped, place pan under the broiler for 1-3 minutes, until cheese is melty and slightly browned, watching closely.