Preheat oven to 350 degrees
To a mixing bowl sift together flour, baking powder and salt. Set aside.
To a separate mixing bowl add melted butter and brown sugar. Whisk until incorporated.
Add the eggs and vanilla to the melted butter and brown sugar. Whisk.
Add the dry ingredients in three batches to the wet. Fold each batch in until mostly incorporated before adding more dry ingredients.
Add the batter to a parchment lined 9x9 pan. Spread evenly.
Mix the cinnamon and sugar together. Drop spoonfulls of the cinnmon sugar on top of the batter. Use a knife to run it through. Smooth the top out before baking.
Bake in the middle rack for 30 minutes.
Remove from the oven and rest. It will continue cooking as it sits. The edges should be set and the middle will jiggle just a tiny bit. It will look puffy but will settle as it cools. Cool for an hour.
While the blondies cool make the icing. Add cream cheese, heavy whipping cream to a pan set over low medium heat. Soften the cream cheese and heavy whipping cream and blend together. Add the powdered sugar to the pan along with vanilla. Continue bringing the icing together with a spatula until there are no lumps. Place in a piping bag or a ziploc with the corner snipped.
Drizzle the icing over the blondies. Cut in 9 squares.