Mix the flour and salt together in a large mixing bowl. Rub in the Trex, using your fingertips, then stir in the easy-blend yeast. Make a well in the middle.
Turn on to a lightly floured surface and knead for 5 – 6 minutes. To knead by hand, fold the dough towards you, then push it away with the heel of your hand. Give the dough a quarter turn and keep kneading, developing a rocking rhythm until it is smooth and elastic.
Turn the dough onto a work surface and knead lightly for 1 minute, so that it is back to its original size. Divide into two equal pieces and roll out into two circles, each 35cm (14in) in diameter. Place onto lightly greased baking sheets and leave in a warm place whilst you make the topping.
Melt the Trex in a frying pan and fry the onion gently for 4-5 minutes, until soft, but not brown. Spread 2 tbsp tomato puree over the base of each pizza. Arrange the onions and tomatoes on top, then sprinkle with the dried herbs, black pepper and cheese.