Preheat oven to 180C/160C fan forced. Grease a 21cm springform pan and line the base with baking paper.
Use electric beaters to beat the butter, sugar and lemon rind until pale and creamy. Add the eggs, one at a time, beating well after each addition. Sift the plain flour and self-raising flour together.
Fold half the flour mixture into the butter mixture until just combined. Fold in milk and lemon juice. Fold in remaining flour. Pour half the batter into the pan and smooth the surface. Cut the pears into long wedges, about 7mm thick. Arrange half the pear slices over the batter. Top with remaining batter and remaining pear slices.
Brush the pears with extra melted butter and sprinkle with extra sugar. Bake for 45 minutes or until golden and cake springs back when gently touched in the centre. Set aside for 10 minutes before turning onto a wire rack to cool completely. Serve.