How to Make It
Beat butter with a stand mixer fitted with a paddle attachment on medium speed until creamy, about 2 minutes. Gradually add powdered sugar, beating until smooth. Beat in vanilla.
Stir together flour, baking powder, and salt in a bowl. Gradually add flour mixture to butter mixture, beating on low speed until combined, about 1 minute. Beat in cranberries and orange zest until just combined, about 30 seconds.
Divide dough in half. Shape each half into a rectangular log about 9 inches long x 2 inches wide x 2 inches tall. Wrap in plastic wrap, and chill at least 2 hours or up to overnight.
Preheat oven to 350°F. Place demerara sugar in a shallow dish. Unwrap dough logs. Gently press demerara sugar into long sides of both logs.
Cut dough into 1/4-inch-thick slices. Arrange slices 1 inch apart on 2 baking sheets lined with parchment paper.
Working in 2 batches, bake cookies in preheated oven until edges are lightly browned, 10 to 12 minutes. Cool on baking sheets 5 minutes. Transfer cookies to wire racks, and cool completely, about 20 minutes. Store in airtight containers up to 1 week.