Preheat oven to 200 deg C. Beat eggs, sugar and vanilla essence, lemon rind and juice until thick. Add sifted flour. Stir until evenly mixed. Gently stir in grapes.
Put in a greased and floured 23cm round tin. Reduce oven to 180 deg C and cook approximately 30-40 minutes. Leave for 3 minutes before turning out.
Dust with sifted Icing Sugar. Serve with a dollop of whipped cream.