Preheat your oven to 375°F (190°C). Line a 9x13 inch baking pan with parchment paper.

In a large mixing bowl, whisk together all-purpose flour, granulated sugar, baking powder, baking soda, and salt until combined.

Add the cold, cubed butter into the dry mix. Use a fork or pastry cutter to cut the butter in until the mixture resembles coarse crumbs.

In a separate bowl, mix buttermilk and vanilla extract together. Pour this mixture into your dry ingredients and stir gently until just combined.

Evenly press your dough into the prepared baking pan to form the base.

In a small bowl, mix together brown sugar and ground cinnamon. Drizzle melted butter over the pressed dough, then sprinkle the cinnamon mixture evenly on top.

Bake for 20-25 minutes until edges are golden brown. Allow to cool completely.

For the cream cheese frosting, beat the cream cheese and softened butter until smooth. Gradually add powdered sugar, milk, and vanilla extract.

Spread cream cheese frosting generously over the cooled bars, cut into squares and serve.