Preheat the oven to 375 degrees F (190 degrees C) and line 2 cookie sheets with baking parchment.

In a bowl, combine the softened butter, superfine sugar, and finely grated lime rind.

Mix the ingredients well with a wooden spoon.

Beat in the lightly beaten egg yolk and orange liqueur (or orange extract).

Sift together the all-purpose flour and a pinch of salt.

Gradually add the flour mixture to the wet ingredients and stir until thoroughly combined.

Scoop tablespoons of the dough and place them on the prepared cookie sheets.

Gently flatten the dough.

Bake for 10-15 minutes, until light golden brown.

Let the cookies cool on the cookie sheets for 5-10 minutes.

Using a metal spatula, carefully transfer the cookies to wire racks to cool completely.

Sift the confectioners' sugar into a bowl.

Stir in enough white tequila to achieve a thick cream consistency.

While the cookies are still on the racks, drizzle the frosting over them with a teaspoon.

Allow the frosting to set completely.