For the pastry, place the flour, butter and sugar into a food processor and pulse until the mixture resembles breadcrumbs. Add one of the eggs and pulse until the mixture comes together to form a rough dough. If the dough is too dry, add a bit of milk. Shape the dough into a ball and wrap in cling film. Chill in the fridge for 20 minutes.
Unwrap the dough and discard the cling film. Turn the dough out onto a floured work surface and roll out until large enough to line a 30x20cm/12x8in cake tin. Line the tin with the pastry, then place into the fridge to chill for a further 30 minutes.
Preheat the oven to 200C/400F/Gas 6.
Line the chilled tart case with a sheet of greaseproof paper and fill with baking beans. Bake for 15-20 minutes, or until the pastry is lightly golden-brown.
Remove the paper and beans and brush the pastry all over with the remaining beaten egg. Return the pastry to the oven for a further five minutes, until golden-brown. Remove the pastry from the oven and turn the oven temperature down to 180C/365F/Gas 4.
For the filling, beat the butter and sugar together in a bowl until pale and fluffy.
Mix in the ground almonds, then crack in the eggs one at a time, beating well between each addition until smooth and creamy. Fold in the lemon zest and the flour.
Spread some of the raspberry jam generously across the base of the pastry, leaving a 2.5cm/1in gap around the edge.
Spread the filling mixture over the jam and sprinkle over the flaked almonds.
Bake the tart for 20 minutes, or until the filling is set and golden-brown. Allow to cool in the tin before serving.
To serve, cut the tart into 5cm/2in squares.