Place the ground almonds, flour sugar and butter in a bowl and rub with your finger tips to form a rough dough.
Using the back of a spoon, press the mixture into the base of a lightly greased 20 cm-round spring form tin lined with non-stick baking paper.
Bake 25 - 30 minutes or until lightly golden. Set aside.
Place the cream cheese, ricotta, eggs, second measure of sugar, lemon juice and rind and vanilla in a food processor. Combine the cornflour and water in a small bowl until smooth and add to the cheese mixture. Process until smooth.
Grease the sides of the cake tin with butter and pour the filling over the base. Tap the tin lightly to remove any air bubbles.
Bake for 1 hour. Turn the oven off and allow the cake to cool in the oven with the door closed for an hour.
Refrigerate until cold. Top with raspberries and blueberries and dust with icing sugar to serve,.