First, make the dukkah, stir the ingredients together and set aside. For the flatbreads, stir the flour, yeast, sugar and salt together in a large bowl. Add 300ml lukewarm water and mix to form a soft, sticky dough. Tip the dough onto a lightly floured work surface and knead for 5 mins until the dough is smooth. Return the dough to the bowl, cover and leave in a warm place to prove until doubled in size, about 1 hr.
Heat the oven to 220C/200C fan/gas 7. Tip the risen dough out onto a lightly floured work surface and divide into four pieces. Roll each piece into a ball, then roll out each ball into a rough oval, around 4mm thick. Carefully transfer the dough ovals to two large non-stick baking trays. Brush with the olive oil and sprinkle evenly with the sesame seeds. Bake for 15 mins until golden and firm to the touch. Transfer the baked flatbreads to a wire rack and leave to cool.
Heat the oven to 220C/200C fan/gas 7. Cut the tomatoes in half through the equator and arrange in a large ovenproof dish, cut-side up. Season with a pinch of sea salt, some black pepper and the sugar, if needed. Drizzle with the oil and sprinkle over the feta and dukkah.
Bake for 20-25 mins until the tomatoes are tender and juicy and the feta is golden, but not too dark. Leave to rest for 5 mins, then scatter over the fresh herbs. Serve warm with the flatbreads alongside.