1. preheat oven to 180°C.
2. In a large bowl combine sugar, butter and vanilla extract and beat until creamy.
3. Zest and juice the lemon, add the zest and 1 tbsp of lemon juice to the butter mixture.
4. Add vinegar and mix thoroughly.
5. Mix flour and baking powder. Gradually mix flour and milk into the butter mixture until you end up with a smooth dough.
6. Pour dough into a lined/greased cake tin (20cm diameter) and bake for around 30 minutes or until golden brown. When poked into the center a skewer or knife should come out clean or with crumbs but not with raw dough.
7. Allow to cool on a cooling rack and serve as is, with your favourite frosting or simply dusted with icing sugar.