Preheat your oven to 180°C (350°F) and lightly grease a 23cm (9-inch) loose-bottomed tart tin.

Unroll the shortcrust pastry and carefully line the tart tin, pressing it gently into the fluted edges. Trim any excess pastry hanging over the rim.

Spread the blueberry jam evenly over the base of the pastry shell, ensuring it reaches the edges.

In a large mixing bowl, beat the softened butter and granulated sugar together until pale and creamy.

Add the eggs one at a time, beating well after each addition. If the mixture starts to curdle, add a tablespoon of the flour.

Fold in the ground almonds, remaining flour, lemon zest, and almond extract until the batter is smooth and combined.

Spoon the frangipane mixture over the jam layer and smooth the top with a spatula or the back of a spoon.

Scatter the flaked almonds evenly over the top of the tart.

Bake in the preheated oven for 35-40 minutes, or until the filling is risen, golden brown, and set in the center.

Remove from the oven and allow the tart to cool completely in the tin before removing.

Dust with icing sugar just before slicing and serving.