Combine 1 cup butter, sugar and egg in bowl. Beat at medium speed, scraping bowl often, until creamy. Add orange juice and 1 tablespoon vanilla. Continue beating, scraping bowl often, until well mixed. Add flour and baking powder; beat at low speed until well mixed.
Divide dough into thirds. Shape each third into a ball; flatten slightly. Wrap each in plastic food wrap; refrigerate 2-3 hours or until firm.
Heat oven to 400°F.
Roll out dough, one-third at a time, on lightly floured surface (keeping remaining dough refrigerated), to 1/8- to 1/4-inch thickness. Cut with 3-inch cookie cutters. Place 1 inch apart onto ungreased cookie sheets.
Bake 6-10 minutes or until edges are lightly browned. Let stand 1 minute on cookie sheet; remove to cooling rack. Cool completely.
Combine powdered sugar, 1/3 cup butter and 1 teaspoon vanilla in bowl. Beat at low speed, scraping bowl often and gradually adding enough milk for desired spreading consistency. Tint with food color, if desired. Frost and decorate cooled cookies as desired.
Variation: Best Ever Butter Cookies with Glaze: Prepare cookies as directed above omitting frosting. To prepare glaze, stir together 2 1/2 cups powdered sugar, 2 tablespoons water, 1 tablespoon Land O Lakes® Butter, softened, 1 tablespoon light corn syrup and 1/2 teaspoon vanilla or almond extract in bowl until smooth, adding additional water, if necessary, to reach desired glazing consistency. Tint with food color, if desired. Glaze cooled cookies. Decorate as desired. Let stand 6 hours or overnight until glaze is hardened.