Preheat your oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.

In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, baking soda, and salt. Add the softened butter and mix until the mixture resembles coarse crumbs.

In a separate bowl, beat together the eggs, vanilla extract, and buttermilk. Pour the wet ingredients into the dry ingredients and mix until just combined.

In a small bowl, combine the ground cinnamon and brown sugar.

Spoon half of the cupcake batter into the prepared muffin cups. Sprinkle a teaspoon of the cinnamon-sugar mixture over the batter in each cup. Top with the remaining batter, dividing it evenly among the cups.

Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean. Allow the cupcakes to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

While the cupcakes cool, prepare the frosting. In a medium bowl, beat together the cream cheese and butter until smooth. Add the vanilla extract and gradually mix in the powdered sugar. If the frosting is too thick, add milk one tablespoon at a time until you reach the desired consistency.

Once the cupcakes are completely cool, frost them generously with the cream cheese frosting.