To make the pastry, put the flour and butter in a large bowl and rub them together with your fingertips until the mixture resembles coarse breadcrumbs. Tip in the sugar, lemon zest and a pinch of salt and mix slightly. Now work in the egg yolk and vanilla extract until you have a smooth dough. Roll the dough into a ball, wrap in cling film and chill for at least 1 hour (or up to 2 days).
While the pastry is chilling, make the lemon crème pâtissière (lemon custard). Put the egg yolks and sugar in a bowl and whisk together using a balloon whisk for 1-2 minutes until the mixture turns pale. Tip in the flour and cornflour and mix well. Put the milk and lemon zest in a saucepan and bring to the boil. Pour the boiling milk over the mixture in the bowl, whisking continuously until everything is smooth.
Pour the custard into the pan, place over a medium heat and simmer for 2 minutes, stirring continuously until it has thickened. Remove the pan from the heat and stir in the lemon juice and butter. Pour the custard into a clean bowl and cover the surface with cling film to stop a skin forming. Leave to cool, then put in the fridge until completely cold. (The custard will keep in the fridge for up to 2 days.)
To make the frangipane (almond cream), tip all the ingredients into a bowl and mix until everything is well combined. (The frangipane will keep in the fridge for up to 4 days.)
On a floured surface, roll out the chilled pastry to the thickness of a £1 coin, then use to line a 25cm loose-bottomed tart tin. Trim the pastry with a small knife but leave a lip hanging over the edge. Chill the tart case for at least 1 hour – if you have room to put it in the freezer, this would be ideal.
Put a baking tray in the oven and preheat the oven to fan 180C/ conventional 200C/gas 6. Using a spatula, stir the crème pâtissière until smooth, then spread three quarters of it over the base of the tart case.
Spoon the frangipane into a piping bag fitted with a smallish nozzle (about 1cm). If you don’t have a piping bag, spoon the mixture into a tough plastic bag, squeeze it into the end, then cut off the tip. Pipe lines of frangipane evenly over the custard. Don’t worry about the gaps, as the frangipane will spread while cooking.
Put the tart tin on the hot baking tray and bake for 30-40 minutes until the frangipane is golden brown and the pastry is biscuity brown. The frangipane will puff up during the baking. Trim off the overhanging pastry with a small knife to give a professional finish. Lift the tart and base from the tin and leave on a wire rack to cool completely.
To make the topping, put the cream in a bowl and lightly whip until billowy. Using a spatula, gently fold the remaining crème pâtissière into the cream, then spread the mixture evenly over the frangipane.
Arrange the raspberries on top, placing them upside down in concentric circles as closely as possible. Put the jam and kirsch in a small pan and bring to the simmer, stirring, until it lightly coats the back of the spoon. Using a pastry brush, gently brush the raspberries with the glaze. Cool slightly, then, using a palette knife, ease the tart off the base on to a serving plate.