Preheat your oven to 350°F (175°C) and grease a 9x13 inch baking pan.

Cream together ½ cup of softened butter, ½ cup of brown sugar, and ½ cup of granulated sugar for 2-3 minutes until light and fluffy.

Beat in 2 room-temperature eggs, ½ cup of sour cream, and 2 teaspoons of vanilla extract until just combined.

In a separate bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking powder, ½ teaspoon of baking soda, 1 tablespoon of ground cinnamon, and ¼ teaspoon of salt.

Gradually add the dry ingredients to the wet mixture and gently fold until no flour streaks remain.

Spread the batter evenly into the prepared baking pan.

Combine 2 tablespoons of granulated sugar and 1 teaspoon of ground cinnamon for the topping and sprinkle over the batter.

Bake in the preheated oven for 25-30 minutes until a toothpick inserted comes out clean.

Allow to cool completely in the pan on a wire rack.

Whisk together 1 cup of powdered sugar, 2-3 tablespoons of milk, and ½ teaspoon of vanilla extract until smooth, then frost the cooled bars.

Slice into squares and serve.