Preheat your oven to 180 degrees C. Grease and line 12 cupcake moulds with paper liners.
Beat butter, sugar and lemon zest with an electric mixer in a large bowl till blended, fluffy and pale yellow.
Add the eggs one by one, beating after each addition. Beat in half the flour, and add buttermilk and lemon juice before beating in the remaining flour.
Drop one round tablespoon of batter into each cupcake mould, and bake cupcakes for 20 minutes or until a toothpick inserted in the centre comes out clean.