Preheat oven to 190°C. Grease a deep 22cm round cake pan; line base and side with baking paper, extending paper 2cm above the edge.
1. Cake Beat the butter, sugar, rind, spices and salt with an electric mixer until fluffy. Beat in the egg until combined. Combine the flour, bicarbonate of soda, almond flour and juice, and fold into the egg mixture. Set aside.
2. Caramel Place the sugar and water in a heavy based sauce pan and stir over medium heat until the sugar is dissolved – simmer but do not bring to the boil. Cook until the mixture forms a caramel. Add the butter and stir until smooth. Pour the caramel onto the base of the cake pan.