Grease, line and grease a 18cm spring-form cake pan. Wrap the outside of the cake pan with aluminium foil to prevent water from seeping into the pan. Preheat oven to 170°C.
Beat cream cheese, butter, sugar, vanilla essence and lemon zest at maximum speed with an electric beater for 5-6 minutes.
Add the egg and egg yolk and continue to beat at maximum speed for 1-1½ minutes until mixture is smooth.
Add sifted flour and baking powder to mix, alternating with the whipping cream. (Make sure that the flour is well incorporated before adding the liquid portion.)
Whisk egg white and salt until foamy then gradually add sugar and lemon juice. Continue to whisk until soft peaks form. Fold in the beaten egg white into the cheese mixture until well combined.
Pour the mixture into prepared pan. Place the cake pan in a larger pan filled to about one-third full with hot water. Bake for 1 hour or until firm and golden. Leave the cheesecake in the oven with the door closed for 25-30 minutes. Remove the water-bath from the oven then leave the cake to cool completely in the oven with the door ajar.
Transfer the cake to a rack. Combine apricot gel and water in a small saucepan and stir over low heat until well dissolved. Glaze the top of the cake with apricot glaze and chill the cake before serving.