Heat the oven to 350 degrees and line a baking sheet with parchment paper.

In a mixing bowl, beat the softened butter and granulated sugar until light and creamy.

Stir in the lemon zest, lemon juice, and vanilla extract until combined.

In a separate bowl, whisk the flour, baking powder, and salt. Add this to the butter mixture and mix until a soft dough forms.

Roll the dough into eight small balls and place them on the baking sheet. Flatten each ball slightly with your hand.

Bake for 10 to 12 minutes until the edges turn lightly golden. Let the cookies cool on the sheet for 5 minutes, then move them to a wire rack.

While the cookies cool, mix the powdered sugar with 1 tablespoon of water to make a thick icing. Add the green food coloring and stir until the color is even.

Spread a small circle of green icing on each cooled cookie to form the iris. Press one candy eye into the center of the icing on each cookie.