1.Preheat oven to 180°C/350°F. Grease deep 20cm (8-inch) round cake pan; line base with baking paper.
2.Make lemon mascarpone frosting. Beat cream, sifted icing sugar and rind in small bowl with electric mixer until soft peaks form. Fold cream mixture into mascarpone. Refrigerate, covered, until required.
3.Beat butter, rind and sugar in small bowl with electric mixer until light and fluffy. Beat in eggs, one at a time (mixture might separate at this stage, but will come together later); transfer mixture to large bowl. Stir in sifted flour, milk and juice, in two batches. Pour mixture into pan.
4.Bake cake about 50 minutes. Stand in pan 5 minutes before turning, top-side up, onto wire rack to cool.
5.Split cold cake into three layers, place one layer onto serving plate, cut-side up; spread with one-third of the frosting. Repeat layering process, finishing with frosting.
Grate the lemon for the frosting before you extract the juice for the cake mixture.Note