Cream the butter and sugar in a bowl for 3–4 minutes until fluffy and smooth. Add the egg and mix well. Sift in the flour and baking powder and stir to combine. Turn the dough onto a lightly floured surface, bring together into a smooth round, and divide in two. Wrap each half in clingfilm and chill for 30 minutes.
Preheat the oven to 180˚C, gas mark 4. In a bowl, beat together the ricotta, honey, vanilla and lemon zest, then fold in the mixed peel. Lightly grease a 20cm loose-bottomed cake tin. Roll out each half of the dough to fit the base of the tin. Press one round into the tin and scatter half the raspberries on top, leaving a 1cm border around the edge. Spoon the ricotta mixture over the raspberries, then place the other round of dough on top and press the edges together.
Bake for 35 minutes until golden and set on top, then allow to cool in the tin for 20 minutes before removing. Serve topped with the remaining raspberries, a good dusting of icing sugar and some whipped cream on the side.