Preheat the oven to 180 C / Gas 4. Grease a 20 cm (8in) cake tin and line with baking parchment.
Beat the butter and sugar together in a mixing bowl until soft, light and creamy.
Separate the eggs and beat the egg yolks into the mixture, then stir in the orange juice and zest.
Sift in the flour, baking powder, salt and spices and fold into mixture. Add the ground almonds and chopped walnuts, and gently stir.
In a separate bowl, whisk the egg whites until stiff and then fold into mixture. Stir in the grated carrots until everything is mixed together, then spoon into cake tin.
Bake in the preheated oven for 75 to 90 minutes until golden, firm to the touch and a skewer inserted into the centre of the cake comes out clean. Remove from the oven and allow to cool in the tin for a few minutes, then place on wire rack to cool completely.