Preheat your oven to 350°F (175°C) and line a cupcake tin with paper liners.

In a medium bowl, whisk together the baking powder, baking soda, salt, and ground cinnamon.

In a large mixing bowl, cream the softened butter and granulated sugar until light and fluffy. Mix in the eggs one at a time, followed by the vanilla extract.

Gradually add the dry mixture to the creamed mixture, alternating with buttermilk until just combined.

In a small bowl, mix the brown sugar, ground cinnamon, and chopped nuts for the swirl filling.

Spoon one tablespoon of batter into each lined cup, add the cinnamon swirl filling, and top with another tablespoon of batter.

Bake for 18-20 minutes until a toothpick comes out clean and the tops are golden.

Cool the cupcakes slightly in the pan before transferring them to a wire rack to cool completely.

Prepare the frosting by mixing softened cream cheese and butter until smooth, then gradually add powdered sugar and vanilla, adjusting with milk as needed.

Once the cupcakes are cool, frost with the cream cheese frosting using a piping bag or spatula.