Line a 9X13 baking dish with parchment paper and spray the paper with a non-stick cooking spray.
In a large mixing bowl, beat together 1 cup softened unsalted butter, 1 cup brown sugar, and 1 cup granulated sugar with a hand mixer or stand mixer until light and fluffy.
Add 2 large eggs and 2 teaspoons vanilla extract. Mix until well combined.
In a separate bowl, whisk together 2½ cups all-purpose flour, 1 teaspoon baking powder, 1½ teaspoons ground cinnamon, and 1 teaspoon salt.
Gradually stir the dry ingredients into the butter mixture until just combined. Do not overmix.
Press this mixture into an even layer in the baking dish. In a small bowl, stir together ¼ cup granulated sugar and 1½ teaspoons ground cinnamon for the topping.
Bake for 25-30 minutes until a toothpick inserted into the center comes out clean.
Allow to cool completely and then cut and enjoy!
Notes
Store the leftovers in an airtight container for up to 4-5 days.