Zest the lime into a bowl and squeeze the juice into a separate container.

Cream the softened butter and one cup of sugar until the mixture is pale and fluffy.

Beat in the egg, vanilla, lime juice, and lime zest until smooth.

Add food coloring if a green tint is desired.

Slowly mix in the flour, baking soda, cream of tartar, and salt until just combined.

Cover and chill the dough in the refrigerator for at least two hours to prevent spreading.

Preheat the oven and line baking sheets with parchment paper.

Scoop dough into tablespoon-sized portions and roll into smooth balls.

Roll each ball in the remaining sugar until fully coated.

Place balls on the baking sheet and bake until the edges are set.

Allow cookies to rest on the hot pan before transferring to a wire rack.