Wash the onion, capsicum, and tomato. Deseed the tomato and cut all three into small cubes.
Spread tomato ketchup evenly on both bread slices, then add a thin layer of mayonnaise.
Top with the chopped veggies, then the grated cheese, then a light sprinkle of chili flakes.
Preheat the air fryer to 180°C (360°F) for 3 to 5 minutes. Cook the bread pizza at 180°C (360°F) for 5 to 7 minutes.
Cook until the edges are golden with a light charred look and the cheese is fully melted.
Serve hot, with extra chili flakes on the side.