Preheat oven to 200C/400F/gas mark 6 and line a baking tray with baking parchment.
To make the crust, add the cauliflower to a pot of boiling water and boil for 5 minutes. Drain, then wrap in a teatowel and squeeze out any excess water.
In a bowl, mix the grated cauliflower with the remaining crust ingredients into thoroughly combined.
Divide the cauliflower mix into four portions and, using your hands, shape the crusts on the sheet. They should be about 1-1½cm thick. Bake for about 30-35 minutes, or until firm and golden.
While the crusts are baking, heat the oil in a frying pan. Add the onion and saute for a few minutes. Add the garlic and stir briefly, then add the rest of the ingredients. Simmer for about 20 minutes, stirring every few minutes.
When the crusts are done, add a spoonful of tomato sauce to each and spread evenly. Add toppings as desired, plus grated cheese.
Bake the pizzas for about 10 minutes at 220C/450F/gas mark 8, until the cheese is golden.
Garnish and enjoy!