1. Mix the flour, salt, sugar and yeast. Stir in 325ml water and the butter (or oil); mix to combine. Tip onto a lightly floured surface and knead for 10 minutes, until smooth (or knead in a freestanding mixer with a dough hook for 5 minutes). Put in a lightly oiled bowl, cover with cling film and leave for 45 minutes- 1 hour, until risen and doubled in size.
2. Knock back the dough; divide into 10 equal pieces. Roll out each to a 0.5cm-thick circle and put on parchment-lined baking trays. Mix the thyme leaves, zaatar and oil together and brush most of it over the dough circles. Toss the tomatoes (or peppers) and feta in the remaining oil, season and divide between the circles, pushing into the dough. Cover with cling film and set aside for 15 minutes.
3. Preheat the oven to 220 ̊C, gas mark 7. Bake the flatbreads for 15 minutes, until golden. Cool on a wire rack before serving.