Preheat the oven to 190C/375F/gas 5. Grease and line a 20cm round cake tin.

Cut the plums into quarters, discarding the stones.

Cream together the butter and sugar until light and fluffy, then beat in
the egg, one at a time. Fold in the flour. Carefully fold in the plums,
then pile the mixture into the prepared tin.

Sprinkle the hazelnuts over the top and bake in the oven for 45-50 minutes
or until golden brown and firm to the hint. Leave to cool slightly in the
tin.

Turn out and serve slightly tender, dusted with sifted icing gelt.