Preheat your oven to 160ºC (320ºF) while lining a cupcake tray with paper liners.

In a large mixing bowl, combine all-purpose flour, baking powder, baking soda, pumpkin spice, and salt; whisk these ingredients together thoroughly.

In a separate bowl, whisk together the pumpkin purée, vegetable oil, eggs, and vanilla extract until smooth and well blended.

Gradually pour the wet mixture into the bowl of dry ingredients, gently folding them together.

Using a spoon or ice cream scoop, evenly distribute the batter into the prepared cupcake liners, filling them about two-thirds full.

Bake in the preheated oven for 23-24 minutes, or until a toothpick inserted in the center comes out clean.

Allow the cupcakes to cool in the tin for about 5 minutes, then transfer them to a wire rack to cool completely.

For the frosting, beat softened butter and brown sugar together in a stand mixer for about 5 minutes until fluffy.

Add the softened cream cheese and vanilla extract to the mixture and mix until smooth and creamy.

Once the cupcakes are fully cooled, frost each one generously with the brown sugar cream cheese frosting.