Chop the onion finely and add it to the potato with the seasoning and the egg. Mix together.
Choose your dish/baking tray, spray with low calorie cooking spray and press the potato into a pizza shape. Bake without the toppings for 30 minutes at 150°C.
After 30 minutes remove the base from the oven and spread on the tomato purée. Sprinkle over the cheese and add your chosen toppings. Bake for a further 10-15 minutes at 180°C.