Heat oven to 400 degrees.
In a large bowl, beat softened butter, 1 ½ cups of the powdered sugar beat until fluffy.
Add in the flour and beat again until incorporated.
Separate the dough into 2 bowls.
Add a drop or two of yellow food coloring and the zest of the lemon to one bowl of dough.
To the other bowl of dough add a drop or two of green food coloring and the zest of the lime.
Mix them until everything is incorporated.
Roll 2 teaspoons of dough into a ball and flatten and place on a parchment paper lined baking sheet.
Repeat with all the dough. You may need to use 2 baking sheets.
These cookies do not spread much.
Bake 6 to 8 minutes or until the edges are just set.
Cool the cookies completely while you make the icing.
In 2 small bowls add ½ cup of powdered sugar in each one.
Add the juice of one lemon into one bowl and the juice of one lime in the other.
Stir until all mixed, this will be a thick glaze but that is what you want.
Spoon a little onto the middle of each cookie.
Garnish with more zest if you like.
Let the icing harden for an hour.
Serve!