01 - Combine cranberries, sugar, water, and orange zest in a small saucepan. Cook over medium heat, stirring occasionally, until cranberries burst and mixture thickens, approximately 6 to 8 minutes. Mash the mixture and cool completely, then blend in a food processor until smooth. Set aside.
02 - Whisk flour, baking powder, and salt in a medium bowl. In a large bowl, beat butter and sugar until light and fluffy, about 2 to 3 minutes. Add egg and vanilla, mixing until combined. Gradually incorporate dry ingredients until just blended.
03 - Divide dough into two halves. Roll each half between parchment sheets into a 10 by 8 inch rectangle, approximately 1/4 inch thick. Spread half the cranberry mixture over each rectangle, leaving a 1/2 inch border along one long edge. Starting from the opposite edge, tightly roll dough into a log and seal the edge. Wrap logs in parchment and chill for at least 1 hour until firm.
04 - Preheat oven to 350°F. Line baking sheets with parchment. Slice chilled logs into 1/4 inch rounds and arrange on sheets, spaced 2 inches apart. Bake 10 to 12 minutes until edges are lightly golden. Cool on baking sheet for 5 minutes, then transfer to a rack to cool completely.