How to make:
Boil a large pan of water. Drop in the spinach. Hold underwater, until limp and wilted. About a minute. Drain and empty into a sieve. Squeeze out any excess liquid (you don’t want the spinach to be watery, so this is worth doing thoroughly).
Take pre-rolled puff pastry. Cut out a 28cm circle – it’s easier if you cut around a circular dinner plate. Transfer to a large, flat baking sheet or tray. Dollop on sour cream. Spread with the back of a spoon. Leave a 2cm border. Scatter with wilted spinach. Follow with crumbled feta and za’atar. Season well.
Chill the pastry for 10–20 minutes – this makes it easier to cut.
Heat the oven to 200C, fan 180, gas mark 6.
Once the pastry is cool, make 8 cuts to create ‘spokes’ – keep an 8cm centre circle.Working with one spoke at a time, pull gently away from the centre (extend the length of each piece). Twist to expose the spinach insides. Aim for 2 twists for each spoke. Brush your tarte with egg.
Bake until risen and well-browned, roughly 25-30 minutes.
Serve warm.