Chop the onion and other vegetables to pieces about 1cm cubes. Heat a frying pan, drain the olive oil from the tuna can into the pan adding the onion,garlic (and optional sun-dried tomato and extra chili).
When the onion is soft, add the capsicum & zucchini and stir until zucchini is starting to cook and remove from heat.
Put a little olive oil around the edge of the pita bread with a pastry brush to ensure the edges don't burn (as the bread is thin it burns easily).
Spread your pizza sauce over the bread.
spread over with a thin layer of cheese (to stop your topping from falling off while you're eating it).
Empty the frying pan contents onto your prepared pita bread bases and add the mushrooms and the tuna.
Scatter the remaining cheese over the pizza and place in the oven for about 20 minutes.