We received some lovely grapefruit marmalade so I decided to use some in a cake. A quick recipe that doesn't involve creaming and it turned out moist and tangy.
225g flour
1 tsp baking powder
pinch salt
115g butter (I used Olivani this time)
85 g sugar (I used brown)
1 tsp orange rind
2 eggs, beaten
3 heaped tbsp marmalade
2 tbsp milk (I used rice)

Preheat oven to 170C. Line a loaf tin with baking paper.
Mix flour, baking powder and salt in a bowl. Rub in butter till it resembles breadcrumbs. Mix in sugar and rind. Then mix in eggs, marmalade and milk.
Pour into your tin and bake for 45-60min until golden brown and cooked through (use the skewer test). Check after 20 min, if it's starting to brown too quickly, cover with foil.
Leave in the tin for a few minutes then transfer to cool on a wire rack. You can drizzle the top with warmed marmalade or apricot jam if you like. I just left mine plain.