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Preheat the oven to 350F. Spray a 9x13-inch pan with cooking spray or line with foil and spray with cooking spray for easy cleanup.
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In a medium bowl, whisk together the baking powder, salt, and flour. Set aside.
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In the bowl of a stand mixer fitted with the paddle attachment, cream together the sugar, brown sugar, and butter. Add the eggs, vanilla, and butter extract, and beat until combined. Add the dry ingredients and mix until combined. Stir in sprinkles.
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Press the dough into the prepared pan. (The dough will be sticky; spray your hands with cooking spray to keep it from sticking it you.) Bake for 22 to 24 minutes. They will be slightly golden, but still have the slightest jiggle in the center. They'll set as they cool. Cool completely before frosting.