Preheat the oven to 350°. Grease an 8 or 9-inch square pan and set it aside. In a medium bowl cream together the butter, orange zest, and sugar. Add the egg and vanilla and beat until combined.
In a separate mixing bowl whisk together 1 ¾ cup of flour, salt, and baking powder. Toss the cranberries in the remaining ¼ cup of flour.
Add the flour mixture to the creamed mixture a little at a time, alternating with the buttermilk, until fully combined. Gently fold in the cranberries.
Spread the batter into the prepared baking pan. Sprinkle with coarse sugar. Bake for 35-40 minutes or until a toothpick comes out clean from the center. Let rest for 15 minutes before topping with the glaze and serving.
Mix the powdered sugar, heavy cream, and orange juice together until smooth. Drizzle across the top of the slightly cooled cake.