Preheat the oven to 170°C.
In a bowl, cream together the butter and sugar.
Add the eggs one at a time, mixing well after each addition.
Sift in the cake flour and baking powder.
Add the yuja marmalade and milk, and mix until well combined.
Pour the batter into a pound cake pan.
Bake in the oven at 170°C for 40 minutes.
Let it cool, then slice and serve.