Set the oven to 390°F (200°C) and let it fully heat while you prep everything else.
Stretch or roll the pizza dough into one large, even round on a baking tray. Brush a thin coat of olive oil around the outer edge so the crust browns nicely.
Stir the tomato sauce with the oregano and a pinch of salt in a small bowl, then spread it over the dough, stopping just short of the edge to leave room for the crust to puff up.
Cover the sauced dough with the grated parmesan, spreading it out in an even layer from edge to edge.
Start at the outer edge and work your way in, ring by ring: halved cherry tomatoes first, then diced yellow pepper with a light scatter of cheddar, then sweet corn, diced green pepper, and finally diced red onion in the center.
Slide the pizza into the hot oven and bake for 15 to 18 minutes, until the crust is golden and crisp at the edges and the cheese is fully melted and bubbling.
Let the pizza cool for a couple of minutes before slicing, then serve warm.