1/2 cup (1 stick) unsalted butter, softened 1 1/4 cup sugar, divided 1 egg 1 tsp. vanilla extract 1/4 cup plus 2 Tbs. buttermilk 1 Tbs. freshly squeezed orange juice 2 cups all-purpose flour 1 tsp. baking soda 1 tsp. finely grated orange zest
Preheat oven to 375°F. In the bowl of an electric mixer fitted with a paddle attachment, cream the butter and one cup sugar at medium speed until light and fluffy, about two to three minutes. Beat in the egg and vanilla. In a small bowl, combine the buttermilk with the orange juice. In a separate bowl, sift the flour with the baking soda. With the mixer on low speed, alternate adding the buttermilk and flour mixtures to the butter mixture, scraping down the sides of the bowl occasionally, until just combined. Chill dough for 30 minutes. Mix the remaining one-quarter cup of sugar and the zest on a small plate. Working one by one, form dough into tablespoon-size balls and roll in sugar mixture, coating well on all sides. Transfer balls to greased baking sheets, placing them one and one-half inches apart. Bake for eight to 10 minutes until cookies are set and edges are lightly browned. Transfer to a wire rack to cool completely.