Use 1 cake tin, approx.: 2.4 litresPreheat the oven to 175 °C. Grease and flour the cake tin. Melt the butter and leave to cool. Whisk the eggs and sugar until fluffy. Combine the flour, baking powder, and lemon zest. Fold the dry mixture into the egg mixture. Add butter, milk and vanilla extract and stir into a smooth mixture. Pour into the cake tin and bake for 50-60 minutes.