For the pastry: Mix together the flour, golden caster sugar and salt in a bowl and then add the chilled and diced butter. Rub this in with your hands until it resembles breadcrumbs, then add the water 1 tablespoon at a time until it begins to come together. Turn the dough out onto a lightly floured work surface, and lightly knead until it forms a uniform dough. Press into a flat round, wrap in clingfilm and put into the fridge for an hour before using.
Roll out the pastry on a lightly floured work surface into a rectangle about 2-3mm thick. Use this to line a 35x11cm loose-based tart tin, then transfer the tart shell to the fridge for 30 minutes, or until firm. Meanwhile, preheat the oven to 180/160C Fan/Gas Mark 4.
For the frangipane: While the pastry is chilling, beat the golden caster sugar and butter together in a bowl using an electric whisk until light and fluffy. Add the eggs one at a time, beating until fully combined before adding the next. Finally add the ground almonds and mix to combine. Set aside until needed.
Line the pastry with a sheet of baking paper, fill with baking beans and bake for 20 minutes. Remove the baking paper and beans, and cook for a further 5 minutes until the pastry is a pale golden brown. Remove from the oven and leave to cool for 5 minutes.
To assemble: Spread the frangipane evenly in the tart shell then add the raspberries in even lines. Sprinkle the tart with flaked almonds, and then return to the oven for 25-30minutes or until golden brown. Remove from the oven and leave to cool in the tin.
For the lemon icing: Combine the icing sugar and lemon juice in a bowl. You can increase or decrease the icing sugar here depending on your preference! Using a small piping bag and tip, drizzle in a criss-cross pattern over the tart.