Preheat oven to 375ºF and line 2 baking sheets with parchment paper.

In a stand mixer fitted with the paddle attachment, cream together the butter and sugar until creamy. Beat in egg and egg white, mixing until combined.

In a medium bowl, whisk together the flour, salt, and baking powder. In a measuring cup, combine the milk, orange juice concentrate and vanilla. With mixer on low, add 1/3 of the flour mixture, followed by 1/2 of the milk mixture. Repeat these steps until you've used up all of the dry and wet ingredients. Mix until just combined.

Using a small cookie scoop or two spoons, drop batter onto the prepared baking sheets, leaving about 2 inches of space between each mound. Bake until the tops are springy and just barely dry, about 7-10 minutes. Allow them to cool on the pan for 5 minutes before transferring to a wire rack to cool completely.

In the bowl of a stand mixer fitted with a whisk attachment, beat the butter on medium-high speed until fluffy. Scrape down the sides of the bowl, then beat in the vanilla and salt.

With the mixer on low, slowly add the powdered sugar and milk, making sure to scrape down the sides of the bowl frequently. Once incorporated, beat on high for at least 3 minutes until light and fluffy. Remove 1/2 of the frosting from the bowl and place in a separate bowl. Return bowl to mixer, add the orange zest, orange extract, and orange food coloring (or red and yellow), and beat until combined.

To get the swirled look, place the frostings in separate pastry bags, then place them both into a larger pastry bag fitted with a large round tip. Pipe the frosting in a circular motion onto one cookie, then top with another cookie.