Preheat oven to 160C, and grease / line a round cake tin with baking paper.
Cream the butter, sugar and lemon zest for 5 minutes, or until pale and creamy. Add the eggs, one at a time, beating well after each addition.
Add the flour, baking powder and yoghurt, and mix until just combined. Spoon into the prepared cake tin, and top with sliced peaches.
Bake for 1 hour, or until an inserted skewer comes out clean. Allow to cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely. Dust with icing sugar to serve.