Preheat the oven to 220°C (200°C fan, gas 7). Unroll the puff pastry and place on a baking tray lined with baking paper. Score a 3cm wide border around the edge with a knife.
Mix the yogurt with sour cream, lemon juice, salt and pepper. Spread over the centre of the pastry, leaving the border clear.
Mix the egg yolk with 1 tbsp water and brush over the edge of the pastry.
Sprinkle with dukkah spice.
Wash and diagonally slice the courgettes. Arrange on the tart.
Sprinkle with the cheese.
Bake for 20 minutes until golden brown. Sprinkle with sesame seeds. Serve warm.