Make lemon butter.Stir ingredients in a medium heavy-based saucepan over very low heat for 10 minutes or until thickened (do not allow to boil or mixture will curdle). Pour mixture into a medium heatproof bowl; cover surface with plastic wrap. Refrigerate several hours or until thick and cold.
2
Preheat oven to 200°C/400°F. Grease a 26cm x 32cm (10½-inch x 12¾-inch) swiss roll pan; line base and two long sides with baking paper, extending paper 5cm (2 inches) over sides.
3
Beat butter, extract and sugar in a small bowl with an electric mixer until light and fluffy; transfer to a large bowl. Add ground almonds and sifted flour; mix well using clean hands.
4
Press two-thirds of the pastry evenly over base of pan. Wrap remaining pastry in plastic wrap; refrigerate.
5
Bake base for 12 minutes or until browned lightly. Cool 10 minutes.
6
Spread lemon butter over base. Crumble reserved pastry over lemon butter; top with flaked almonds.
7
Bake slice for 25 minutes or until browned. Cool in pan; refrigerate until cold. Remove from pan; cut into 16 pieces. If you like, dust with a little sifted icing (confectioners') sugar before serving.