Heat your oven to 200 degrees, and spray a loose bottomed quiche tin liberally with low calorie cooking spray.
Add the minced beef to a bowl, and with a fork, mix in the egg, oregano, chilli powder, and a generous pinch of salt and pepper.
Add the meat mixture to the quiche tin, and use the back of your fork to flatten firmly, so that it forms your pizza base.
Cook the base in the oven for ten minutes.
Drain any excess water off your tinned tomatoes, and spread over the base. Add three quarters of your mozzarella, and arrange the mushrooms, peppers, and onions on top. Sprinkle over the remainder of your mozzarella.
Put your meatzza back in the oven for 10 minutes, or until the mozzarella is melted and your meat base is cooked through.
Arrange your basil leaves on top of the meatzza, and transfer to a board or plate.
Slice, serve with your choice of sides, and enjoy!