Preheat oven to 180°C. Line 24 muffin tins with cupcake papers.
Cream the butter in a large bowl with an electric mixer until soft. Gradually add the sugar and grated lemon zest and beat until the mixture is light and fluffy.
Add the eggs in one at a time, beating between each addition.
Sift in the flour and baking powder and fold into the mixture.
Spoon the mixture into prepared muffin tins and fill approximately 3/4 full. Bake for approximately 15 minutes, until risen and golden.
Remove the cupcakes from the tin and place on a wire rack to cool before you ice them.