1. Preheat the oven to 180°C and grease and line a loaf tin (22x13cm) with baking paper.
2. Mix together the flour, baking powder, xylitol and lemon zest in a large bowl.
3. Mix the eggs, sunflower oil, milk and yoghurt together in a separate bowl, before stirring into the flour mixture.
4. Spoon into a tin and smooth the surface. Transfer to the oven immediately, bake on the middle shelf of the oven for 60–70 minutes. Check after 50 minutes: if the cake is becoming too dark, cover loosely with foil.
5. Just before the end of cooking time, make the drizzle by heating the lemon juice and xylitol. Stir over a low heat until the xylitol has dissolved. Once the cake is cooked, take it out of the oven and pour over the drizzle.