Place the flour, yeast and salt in a large bowl. Combine half the oil with the measurement water and stir into the flour to form a dough.
Turn the dough out on a lightly floured surface and knead for 5 minutes until smooth and elastic. Place in a lightly oiled bowl, cover with a damp cloth and set aside in a warm place for about 1 hour until doubled in size.
Meanwhile, heat the remaining oil in a frying pan, add the onion and fry for 7–8 minutes until softened and golden. Leave to cool.
Turn the risen dough out on the floured surface and add the remaining ingredients, including the onion, kneading it into the dough. Shape into an oval, place on a lightly floured baking sheet and leave to rise for 1 hour.
When the loaf has risen, slash a few cuts in the top, sift over a little flour, then bake in a preheated oven, 220°C (425°F), Gas Mark 7, for about 25 minutes until hollow-sounding when tapped. Transfer to a wire rack to cool.