Prepare the pizza dough and set to rise in a warm place. Preheat the oven to 240 C and if using a pizza stone put into the oven to warm for 20 minutes.
Shape the dough and place on a pizza pan. Brush with the garlic oil and top with the red onion.
Add the cheeses followed by the tomato slices. Season with salt and pepper.
Bake the pizza in the oven until the edges and bottom are nicely browned and the cheeses are melted. This should take about 8-12 minutes.
Remove from the oven and sprinkle with the marjoram. As the cheeses will be quite runny let the pizza sit for a couple of minutes before slicing.