In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and sugar until light and fluffy, 3 to 4 minutes. Add the egg, and beat just until blended. Beat in zests, juice, and almond extract. On low speed, add the flour and cornmeal, and beat until well combined. Remove dough to a piece of plastic wrap. Wrap, and chill until firm, about 1 hour. Heat the oven to 350 degrees F. Line 2 baking sheets with silpats (French nonstick baking mats) or parchment paper. Using a 1 1/4-inch ice cream scoop, form balls of dough about 3 inches apart on the prepared baking sheets. Flatten balls with the bottom of a glass dipped in cornmeal to 1/4-inch thick. Bake until crisp and light golden brown around the edges, 14 to 16 minutes. Transfer to a wire rack, cool completely. Place a wire rack over a sheet of parchment paper. Spoon a little of the glaze onto each cookie, allowing any excess to drip off the edges. Store in an airtight container up to 3 days.
Place all the ingredients in a medium bowl, stirring until well combined. Use immediately. Yield: about 1 1/3 cups