Preheat the oven to 350°. Wrap the outside of a 9-inch springform pan with foil to prevent leaking; butter the pan. In a saucepan, stir 4 tbsp. butter and the brown sugar over medium heat until melted and smooth, 2 to 3 minutes; pour into the prepared pan. Scatter the cranberries over evenly.
In a food processor, pulse the flour, walnuts, baking powder, cinnamon, and salt until the nuts are finely ground. In a large bowl, using an electric mixer on medium speed, beat the remaining 8 tbsp. butter, the sugar, and zest until light and fluffy, about 2 minutes. Beat in the eggs, 1 at a time, until blended. Beat in the vanilla. Alternately add and beat in the dry ingredients in 3 additions and the buttermilk in 2 additions, starting with the dry ingredients and stopping to scrape down the sides and bottom of the bowl between additions. Pour the batter over the cranberries.
Bake the cake until a toothpick comes out clean when inserted into the center, about 1 hour and 10 minutes. Let cool for 15 minutes. Run a knife around the sides of the pan to release the cake. Release the pan sides. Place a plate on top of the pan. Using oven mitts, invert the cake onto the plate. Serve warm or at room temperature.
This recipe is part of our Southern-Style Ham & Biscuits holiday dinner menu. Get the rest of the recipes here.