Preheat oven to 200 C / Gas 6. Lightly grease a pizza tray.
For the pizza dough:
Sift flour and salt into a warm mixing bowl and let stand in a warm place. Combine the milk and water and add the sugar and yeast. Whisk with a fork and leave in a warm place for 10 to 15 minutes.
Make a hollow in the flour and add the egg together with the yeast mixture. Gradually work all of the ingredients together, gradually including more and more of the flour. Turn out onto a flour-dusted work surface and knead thoroughly. Put soft, spreadable butter into the centre of the dough and knead for a further few minutes. Put into a greased bowl, cover with cling film and leave in a warm place for 40 minutes.
For the tomato sauce:
Meanwhile prepare the tomato sauce. In a saucepan, heat the oil and cook and stir the onion until soft. Add the tomatoes and cook until pulpy, season.
Roll out the pizza dough and transfer to the prepared pizza tray. Add tomato mixture to within 5mm (1/4 in) of the edge. Leave to prove for 5 minutes. Arrange your favourite toppings on the pizza.
Bake in the preheated oven for 30 minutes.
If you are in a time crunch, you can substitute the fresh tomatoes for tinned tomatoes.