1 1/2 tablespoon tablespoons lemon juice, approximately
Preheat the oven to 160°C (140°C fan-forced). Grease a deep 20cm square cake pan; line the base with baking paper.
Beat the butter, extract, rind and sugar in a small bowl with an electric mixer until light and fluffy. Beat in the eggs, one at a time, until well combined. Transfer mixture to a large bowl. Stir in the ground almonds and sifted flour. Spread mixture into the prepared pan; smooth the top. Bake for 1 hour or until a skewer inserted into the centre comes out clean.
Meanwhile, combine the extra sugar and juice in a small saucepan; stir over a medium heat until the sugar is dissolved. Remove from the heat.
Prick the surface of the cake all over with a skewer. Pour the hot syrup over hot cake. Allow the cake to cool in the pan.
Make the lemon glaze. Combine sifted icing sugar and lemon juice in a small bowl until smooth. Transfer the cake to a serving plate; spoon over the lemon glaze.