Combine coconut, condensed milk, and sugar in a large sauce pan. Gently simmer until it reaches the "soft ball stage" which is 235F-245°F.
When the mixture is the right temperature stir in the butter and lemon rind. Allow to cool to room temperature and then beat the mixture until it is thick and glossy. Pour into the pan lined with foil and chill. Once it is chilled, cut into small squares.