In a small bowl, zest all the citrus fruits. Remove about 2 teaspoons of zest and place in a separate bowl. Add 1/2 cup of granulated sugar to the 2 teaspoons of zest. Use a fork to combine and set aside.

In a mixing bowl, add the softened butter and remaining 1 cup sugar. Beat for 1-2 minutes. Add the egg and beat until combined. Mix in the flour, baking powder, and baking soda. Gradually add the zest and sugar mixture and beat until smooth.

Preheat oven to 350°F. Line a baking sheet with parchment paper. Roll cookie dough into 3/4 to 1-inch balls. Roll each ball in the sugar and zest mixture, and then place on the prepared baking sheet.

Using the bottom of a glass, gently flatten each cookie to about 1/4 inch thickness. Optional: sprinkle a little extra sugar on top.

Bake for 10-12 minutes or until edges are golden. Remove from oven and cool on wire racks.