Preheat the oven to 375°F (180°C or 170°C for a fan oven).
Lightly butter a 9 x 13 inch rectangular tart pan with a loose bottom.
Line the pan with the pastry, making sure it goes up the sides. Prick the pastry with a fork several times and bake for 8 to 10 minutes or until it is just beginning to cook without taking on any colour.
Remove the pastry from the oven and set aside to cool.
Mix the ground almonds, flour, baking powder and salt together in a medium bowl. Set aside.
Cream the butter and sugar in an electric mixer.
Add the eggs, one at a time, beating after each addition and scraping down the bowl as necessary.
Beat in the lemon rind and lemon extract.
With the electric mixer on low, add the ground almond and flour mixture spoonful by spoonful. Beat the mixture for a minute or two until smooth.
To assemble the tart, spread the lemon curd over the bottom of the pastry using a pastry brush and top with the blueberries.
Dollop the cake mixture in medium size spoonfuls over top of the blueberries and gently spread it to cover them, right up to the edges of the pastry.
Scatter with the flaked almonds and bake for 25 to 30 minutes (watching carefully so that it doesn't go too brown). The tart is cooked when the filling bounces back when lightly pressed with your finger.
Remove from the oven and cool completely before cutting in squares to serve.