01 - Preheat oven to 350°F. Grease and flour a 9-inch round cake pan.
02 - In a large bowl, whisk together flour, sugar, baking powder, baking soda, salt, and cinnamon until well blended.
03 - Beat softened butter until creamy. Add eggs one at a time, mixing thoroughly after each addition.
04 - Stir buttermilk, vanilla extract, apple cider vinegar, and orange zest into the butter mixture until combined.
05 - Gradually add wet ingredients to dry ingredients, mixing until just combined. Avoid overmixing.
06 - Gently fold golden raisins and walnuts into the batter until evenly distributed.
07 - Transfer batter to prepared pan and smooth top with spatula.
08 - Bake for 40-45 minutes until toothpick inserted in center comes out clean.
09 - Let cake cool in pan for 10 minutes, then turn out onto wire rack to cool completely.
10 - Serve plain, dusted with powdered sugar, or with whipped cream.