Start by making the pastry – you can do this a few days ahead, if you like. Tip the flour into a large bowl and add the butter and a good pinch of salt. Use your fingertips to rub the butter into the flour until you have a damp, sandy texture. Add the egg and 1 tbsp cold water, whisk together with a fork, then work the egg into the buttery flour crumbs until the pastry comes together, adding a splash more water if it seems dry. Don’t overwork the pastry otherwise it will become tough. Shape the pastry into a disc, wrap in parchment or a beeswax cloth, then chill until you’re ready to use it. Will keep frozen for up to three months.

Now make the filling. Heat the oil in a large frying pan over a low-medium heat, add the sliced onions and a pinch of salt. Cook slowly, stirring now and then, until the onions are soft, about 10-15 mins. Add the vinegar, sugar and chilli and cook for another 5-10 mins until the onions are sticky and caramelised. Stir in 1 tbsp za’atar. Remove from the heat and leave to cool.

Remove the pastry from the fridge. If it is very firm leave it at room temperature for 30 mins to make rolling easier. Heat the oven to 200C/180C fan/gas 6 with a baking sheet on the middle shelf to warm up. Place a large piece of baking parchment (roughly the size of the baking sheet) on your work surface and dust with a little flour. Roll out the pastry on the parchment to a circle roughly 32cm in diameter and about the thickness of a £1 coin.

Spread the caramelised onions over the centre of the pastry, leaving a 1cm border around the edge. Break off small chunks of goat’s cheese and scatter over the onions, then scatter over the thyme leaves too.

Fold the pastry edge inwards to create a border around the tart, leaving the onion filling exposed. Brush the pastry with egg yolk and sprinkle the remaining za’atar on the crust. Remove the tray from the oven and slide the sheet of parchment and the tart on top. Return to the oven and bake for 40 mins until golden brown. Leave to cool for 5-10 mins before serving.