- Heat the oven to 180°C/gas 4 and lightly grease a 20cm x 25cm cm cake tin with the rapeseed oil.
- In a bowl, mix the flour, baking powder and spice together.
- In another bowl add egg and banana and beat well. Mix in the sweetener and oil.
- Gradually fold the dry ingredients into the banana, egg and oil mixture, then fold in the sultanas and carrots.
- Pile the mixture into cake tin and bake for 25-30 minutes then remove from the oven and allow to cool on a wire rack.
- When the cake is cool, cover with the sweetened quark and top with orange zest and walnut pieces.
- Make sure the cake is completely cooled before topping otherwise the cream cheese will melt.
- Try cutting into small squares before you top it, then pipe a blob of sweetened cream cheese onto each square and sprinkle with orange zest and a piece of walnut.
- You could use cinnamon in place of mixed spice or try using different nuts such as hazelnuts or almonds.