1.Combine yeast, sugar, 1 tablespoon of the flour and the water in small bowl; whisk until yeast dissolves. Cover; stand in warm place about 10 minutes or until mixture is frothy.
2.Combine remaining sifted flour and salt in processor; pour in combined yeast mixture and oil while motor is operating. Process until dough forms a ball. Turn dough onto floured surface; knead 10 minutes or until dough is smooth and elastic. Place dough in oiled large bowl. Cover; stand in warm place about 30 minutes or until dough doubles in size.
3.Turn dough onto surface sprinkled with half of the semolina; knead 1 minute. Place dough on oiled large oven tray sprinkled with remaining semolina; press dough into a 32cm square.
4.To make tomato sauce, heat oil in medium saucepan; cook onion and garlic, stirring, until onion is soft. Stir in undrained crushed tomatoes, paste, basil and sugar; simmer, uncovered, about 5 minutes or until thickened.
5.Boil, steam or microwave silverbeet until wilted. Drain; cool. Squeeze as much liquid as possible from silverbeet; chop silverbeet finely. Spread pizza base with tomato sauce. Spread evenly with silverbeet, cheeses and tomato. Bake in oven at 230°C for about 20 minutes.