Preheat oven to 180°C. Brush a round 20cm (base measurement) cake pan with melted butter to lightly grease. Spread almonds over a baking tray. Cook in oven, stirring occasionally for 3 minutes or until toasted. Remove from oven and set aside.

Use an electric beater to beat together the butter and sugar in a large bowl until pale and creamy. Add the eggs 1 at a time, beating well between additions, until thick and creamy. Stir in half the flour, then half the buttermilk until just combined. Stir in the remaining flour and buttermilk along with the orange rind and orange juice until combined. Spoon into the prepared pan and smooth the surface. Bake in oven for 35 minutes or until a skewer inserted into the centre comes out clean. Remove from oven and set aside for 5 minutes before turning onto a wire rack for 30 minutes or until cooled. Place on a serving plate.

To make the icing, use an electric beater to beat together the sour cream and icing sugar in a medium bowl until combined.

Spread the icing over the cake and sprinkle with toasted almonds. Cut into wedges to serve.