These crinkle cookies straddle the line between cake and shortbread with a lovely citrus note from calamondin oranges -- a cross between tangerines and tart kumquats.
Preheat the oven to 350°. Line two baking sheets with parchment paper and set aside.
In a medium bowl, combine the flour, baking powder, salt and zest. Whisk to combine and set aside.
In a large bowl, cream the butter and sugar together with a hand mixer until light and fluffy. Beat the eggs into the sugar mixture one at a time. Add the juice and food coloring and mix again. Gradually add the flour mixture to the sugar mix, just until the flour is incorporated.
Cover with plastic wrap and refrigerate the dough for 30 minutes or until firm.
Use a one tablespoon measure to portion out dough. Roll each portion into a ball and set on a piece of parchment paper. Continue in this way, until all the dough is rolled into balls.
Add the confectioners sugar to a shallow bowl and roll each of the balls in the sugar until well coated. Transfer to the prepared baking sheets setting the balls about 2 inches apart, so there's room to spread.
Bake for 15-18 minutes or until lightly browned on the bottom. Transfer cookies to a wire rack to cool. Store in an airtight container, separated by sheets of plastic wrap.