In a medium-sized bowl, sift together the baking powder, salt, cornstarch, and cinnamon with the flour.
Preheat your oven to 325°F (163°C). Line an 8 x 8-inch (20 x 20 cm) baking pan with parchment paper, spray it with non-stick cooking spray, and set it aside.
In a large mixing bowl, whisk together the melted butter and brown sugar until well combined.
Add the eggs and egg yolk one at a time, whisking after each addition. Stir in the vanilla paste (or vanilla extract).
Gently fold the dry ingredients into the wet mixture until no streaks of flour remain. Be careful not to overmix.
Pour the blondie batter into the prepared pan.
Create the cinnamon sugar swirl by combining the ground cinnamon and brown sugar. Sprinkle generous amounts of the cinnamon sugar mixture over the blondie batter. Use a toothpick to create big swirls.
Bake for 30 to 40 minutes or until the blondies are golden brown, set around the edges, and have slightly puffed up. This should take around 35 minutes. The center will still be a bit doughy, but they will continue to cook as they cool. Allow them to cool for about 30 minutes.
While the cinnamon roll blondies are cooling, prepare the cream cheese icing.
In a small microwaveable bowl, melt the butter.
For the cream cheese icing
In a stand mixer fitted with the paddle attachment, beat the cream cheese for about 30 seconds. Add the melted butter and continue beating. Then, add powdered sugar, vanilla extract, and a pinch of salt. Beat until well combined.
Once the cinnamon roll blondies are completely cool, drizzle them with the cream cheese glaze by putting the glaze in a ziplock bag and cut a small corner off.