In a large mixing bowl or the bowl of your stand mixer fitted with the paddle attachment, cream the butter and sugar until light and fluffy. Beat in the lemon zest, apple purée, baking powder, salt, and flour until combined. Stir in the milk and lemon juice until the batter is smooth.
Bake for 12-15 minutes or until a toothpick inserted into the center comes clean.
Cool in pan for a few minutes before transferring to a wire rack to cool completely. Glaze.