In a medium mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, poppy seed, and baking soda; beat until combined, scraping sides of bowl occasionally. Beat in egg yolk, milk, lemon peel, and vanilla until combined. Beat in as much of the flour as you can with the mixer. Using a wooden spoon, stir in any remaining flour.

Divide dough in half. Shape each half into a 9-inch-long roll. Wrap in plastic wrap or waxed paper. Chill in the refrigerator for 4 to 24 hours. Using a sharp knife, cut dough into 1/2-inch slices. Place slices 1 inch apart on ungreased cookie sheet.

Bake in a 375 degree F oven for 7 to 9 minutes or until edges are firm and bottoms are light brown. Place powdered sugar in a plastic bag. If desired, add edible glitter to powdered sugar. While still warm, transfer several at a time to the bag. Gently shake until coated. Transfer cookies to a wire rack; cool. When completely cool, gently shake cookies again in powdered sugar. Makes 36.

Bake and cool cookies as directed. Do not coat with sugar. Place in freezer container; seal and freeze up to 3 months. Thaw about 15 minutes. Shake in powdered sugar as directed.