Pre heat the oven to 200 degree C/ 392 F, I use a fan assisted electric oven please adjust according to your own oven.
Add the flour to a large bowl. Add the salt to one side of the flour then add the yeast and sugar to the other side. Make a well in the middle and pour in the warm water and olive oil. Mix with a spoon until you have a wet dough.
Turn the dough out into a floured surface and knead for 5 minutes, add a little olive oil to the bowl then place the dough in the bowl. Cover with cling film and a tea towel then leave in a warm place for the dough to rise. In warm weather this should only take about 30 minutes.
Then turn out the dough onto a floured surface and knead again for a couple of minutes.
Divide the dough in half, using your knuckles make an edge in the dough then pull the dough out to make a good size round.
Sprinkle an oven tray or pizza stone with polenta, place the pizza base on the tray.
Mix the ricotta and garlic, then spread half the ricotta on the pizza base, add half the mozzarella then sprinkle 1 tbs of dried oregano over the cheese,
Add half the onions and top with half the spinach and tomatoes drizzle 1 tbs of olive oil over the pizza and season with a little cracked black pepper.
Place on the top shelf of the oven and cook for 10 to 15 minutes until the cheese is golden, the tomatoes are burst and the base is cooked.
Repeat for the next pizza.
Serve with basil leaves and generous shavings of parmesan cheese.