Preheat the oven to 400 degrees.
Chop the walnuts into small pieces. Place them in a separate bowl and set that aside.
In a medium bowl, combine flour, baking soda, cinnamon, and baking powder. Mix the flour mixture together to combine and set that aside.
In a large mixing bowl, add the sugar and melted butter. Add the eggs, and buttermilk. Mix well to combine.
Add the dry ingredients to the wet ingredients and mix until just combined. The batter will not be smooth, it’s ok if there are a few lumps.
Pour the chopped walnuts and the dried cranberries to the batter. Fold them in until just combined.
Line a muffin pan with the paper liners. Scoop equal amounts of batter into the muffin tins. Sprinkle a teaspoon of brown sugar on top of the muffins before baking.
Set the baking time to 22 minutes and bake until the tops are golden brown or until a toothpick is inserted and comes out clean.
Allow the muffins to cool slightly on a wire rack and serve.