Preheat oven to 350 degrees F. Liberally grease a 9x13 rectangular baking pan with cooking spray; set aside.

In the bowl of a stand mixer, combine the granulated sugar, pumpkin, oil, vanilla extract, and eggs and beat slowly with the paddle attachment until blended, about 30 seconds. In a medium bowl, whisk together the flour, baking powder, baking soda, spices, and salt until combined and gradually add in the flour mixture to the pumpkin wet mixture until the batter comes together. Pour the batter evenly into the prepared pan and smooth out the top.

Bake the cake for 25-30 minutes or until a toothpick inserted near the center comes out clean or with moist, not wet, crumbs. Cool completely.

For the frosting: Add the butter to a small saucepan. Cook over medium-low heat, stirring occasionally, until melted. Stay close as the butter begins to bubble up, foam and sizzle as this is when it begins to brown. Swirl the pan occasionally to allow the butter solids to separate and caramelize on the bottom, about 5 minutes. The second you see browned bits on the bottom and detect a nutty aroma with your nose, it is done. Do not walk away for risk of burning the butter! Remove from the heat and cool completely.

In a medium bowl, combine the confectioners' sugar, milk or heavy cream, and pure maple syrup. Add in the browned butter, ensuring you get the browned bits on the bottom of the pan! Mix well until a soft and spreadable frosting comes together. Spread the frosting over the cooled cake and serve. I like to refrigerate my frosted cake covered and serve it cold, but it can be served right away.