Add the flour and butter to a bowl and rub in with your fingertips or an electric mixer until you have fine crumbs. Stir in the icing sugar, almonds and lemon rind, then the egg yolks, and mix to form a dough. Chill for 15 minutes.
Knead the pastry, then cut off and reserve a quarter. Roll out the remainder thinly on a lightly floured surface to fit a buttered 24 cm (9½ inch) fluted loose-bottomed tart tin. Press the pastry over the base and sides of the tin. Trim off the excess and add the trimmings to the reserved pastry. Chill the tart and trimmings for 15 minutes.
Add the redcurrants, lemon juice and sugar to a pan and simmer for 5 minutes until the redcurrants are soft. Stir in the cornflour paste and cook over a high heat, stirring until the fruit compote thickens. Leave to cool.
Spread the redcurrant compote over the tart base, then sprinkle the raspberries over the top. Brush the pastry edge with water. Roll out the trimmings and cut into 1 cm (½ inch) wide strips and arrange as a lattice over the tart, pressing the edges but not trimming off the excess.
Bake the tart on a baking sheet in a preheated oven, 190°C (375°F), Gas Mark 5, for 25–30 minutes until the pastry is golden and the base is cooked. Trim off the excess pastry from the lattice. Warm the redcurrant jelly in a small pan on the hob or in the microwave and brush over the pastry lattice, then leave to cool. Remove the tart from the tin, transfer to a serving plate and serve.