Roll the pastry out on a lightly floured surface to the thickness of a pound coin. Use to line a deep, 23cm fluted, loose-bottomed tart tin. Trim the excess and prick the base all over with a fork. Chill for 30 minutes.
Meanwhile, make the crème pâtissière. Put the milk and vanilla pod in a large pan, bring to the boil, then turn off the heat. In a large bowl, whisk the yolks and sugar for 10 minutes until voluminous, then beat in the flour and lemon zest. Strain the warm milk slowly into the egg mixture, whisking continuously. Clean the pan, then pour the mixture back in and gently bring to the boil, stirring constantly until it has thickened. Take the pan off the heat, cover the surface of the crème pâtissière with baking paper and leave to cool.
Preheat the oven to 180°C/fan160°C/gas 4. Line the pastry case with baking paper and fill with baking beans or rice. Place on a baking sheet and blind-bake for 15 minutes. Remove the beans/rice and paper, then cook for a further 10-15 minutes until golden. If the edges look too dark, cover with foil. Leave for 5 minutes, then transfer to a wire rack to cool completely.
Spoon the crème pâtissière into the tart, then level the surface with the back of a spoon. Place a strawberry half in the centre of the tart, then arrange concentric rings of fruit around it until all of the crème pâtissière is covered.
Gently warm the jelly with 2 tbsp water until melted, brush over the strawberries and leave for 2 minutes to set.