1/2cup(1 stick) unsalted butter, melted and cooled slightly
3/4cupgranulated sugar, divided
1/3cuplight brown sugar, packed
1/2teaspooncream of tartar
Preheat oven to 350°F. Prepare an 8-by-8-inch baking pan by spraying it lightly with non-stick spray, lining it with parchment paper so that the paper slightly overhangs, and spraying lightly again; set aside.
In a large bowl, combine melted butter, egg, ½ cup granulated sugar, brown sugar, and vanilla, and stir or whisk until smooth.
Add flour, cream of tartar, andl salt; stir until just combined.
Scrape batter into prepared pan, smoothing the top; set aside.
In the same bowl, combine ¼ cup sugar and cinnamon. Sprinkle cinnamon sugar evenly over the top of the dough.
Bake 24 to 25 minutes, or until a toothpick inserted in the center comes out clean, or with a few moist crumbs.
Place pan on wire rack to cool for at least 15 minutes. Lift bars out of pan using parchment paper, and cut into 16 servings.
If desired, double all ingredients and use a 9x13 inch pan. Increase cooking time to 30-35 minutes or until a toothpick inserted in the center comes out clean, or with a few moist crumbs.
Bars can be frozen up to 3 months in airtight container.