Put the flour, yeast, sugar and salt into a large bowl and blend them together.
Separate the egg, add the yolk to the bowl and save the white for later.
Stir the water into the bowl and when everything looks craggy and lumpy, stir in the oil.
Use your hands to bring everything together into a stiff ball of dough and knead for 100 presses.
Cover the dough with oiled cling film and leave it in a warm place for the dough to double in size, which will take about an hour.
Line a baking tray with parchment.
Roughly chop the tomatoes and add them to the dough bowl.
Squeeze and press the tomatoes into the dough as you knead the dough for another 100 presses.
Divide the dough into three equal pieces and roll each into a 40cm/16” strand.
Lay the three strands in front of you and pinch the furthest ends together.
Plait the dough by gently lifting the right-hand strand over the middle strand to become the middle one. Then cross the left-hand strand over the new central strand so that it becomes the middle strand. Continue lifting right and left hand strands over the central one and pinch the ends together to finish.
Gently lift the plait onto your prepared tray and brush with the reserved egg white.
Leave the plait to rise in a warm, draught free place for 25 minutes.
Pre-heat the oven.
Bake for 35-40 minutes until plump and golden.
Carefully transfer the plait to a rack and leave to cool.