Preheat oven to 165 deg C. Grease a 9 x 5 inch loaf pan with butter or cooking spray. Sift plain flour and baking together, set aside.

Beat butter, lemon zest and sugar until pale and fluffy at medium speed for about 7-8 minutes. Reduce speed, add vanilla extract. Add eggs, one at a time beating thoroughly after each addition.

Add in half of the flour followed by the sour cream and remaining flour, beating until just incorporated.

Pour in half of the batter into loaf pan, smoothen the batter and add about 2 tbsp yuzu marmalade on top and spread evenly with a spatula. Lastly pour in the remaining half of the batter and smooth top again with a spatula.

Bake in the preheated oven for about 70 minutes or a skewer into the center of the cake comes out clean.

Leave cake to cool in loaf pan for 10 minutes, then turn out cake onto rack to cool completely.

recipe adapted from here