Whisk eggs in a bowl. Add yogurt, sugar, milk, oil, flour, and baking powder. Mix thoroughly.
Gently fold in raisins, diced apple, lemon juice, and zest.
Pour batter into a greased cake pan.
Sprinkle grain sugar on top for added sweetness and crunch.
Bake at 180°C for 35-40 minutes or until a toothpick comes out clean.
Allow to cool, then spread jam or marmalade on top.