Brown the Butter

Melt the butter in a saucepan over medium heat. Swirl the pan occasionally to be sure the butter is cooking evenly. As the butter melts, it will start to turn from yellow to a deeper golden color and toasty brown bits will start forming around the edges. When the butter starts to foam up and give off a nutty aroma, the brown bits will start to really show up. Take it off the heat immediately to avoid burning. Pour the butter and scrape the browned bits into a heatproof bowl or liquid measuring cup to cool down for about 15 minutes.

Mix the Cinnamon Sugar Topping

In a small bowl, mix together the cinnamon sugar topping and set aside.

Mix the Snickerdoodle Blondies

Preheat oven to 350°F. Line 9x9x2-inch metal baking pan with parchment paper, extending over the edges a bit so you can lift the baked Blondies out of the pan. Alternatively, you can grease the pan.

In a medium bowl, whisk together the flour, baking soda, cream of tartar and salt. Once the brown butter is cool to the touch, combine the butter with the granulated sugar and brown sugar in a medium sized mixing bowl and whisk together until combined. Stir in the eggs and vanilla until completely combined.

Using a spatula, fold in the dry ingredients and mix until just combined.

Spread the blondie batter into the prepared pan, using a spatula or your hands to press it evenly into the pan. Sprinkle the cinnamon sugar topping over the top of the Blondies.

Bake & Serve

Bake until a tester inserted in the center comes out with just a few crumbs, somewhere between 25-30 minutes. The edges should be a deep golden color and look firm. The center should still be moist but not gooey.

Allow Blondies to cool in the pan for at least 20 minutes. Use the parchment paper to lift blondies from the pan. Cut into a 4x4 grid and serve!