Preheat the oven to 350 degrees F.
Sift the flour into a large bowl. See Tips & Tricks below for information on how to correctly measure and sift your flour.
Add the baking powder, baking soda, cinnamon, nutmeg, ground cloves, and a pinch of allspice to the flour and gently whisk to combine. Set aside.
Cut the butter into tablespoon size pieces (doesn't have to be exact) and add to a small, microwave-safe bowl. Melt the butter in the microwave starting with 30 seconds. It is ok if a few small, unmelted pieces remain.
Add the melted butter, granulated sugar, and packed brown sugar to the bowl of a stand mixer fitted with a paddle attachment. Mix on low speed until thoroughly combined, about one minute.
Crack the eggs into a cup and transfer to the butter and sugar mixture. Mix on low speed until combined.
Add the vanilla extract and mix in.
Mix in the sour cream and milk.
Slowly add the dry ingredients, 1/2 at a time. Mix on low speed, scraping down the sides of the bowl with a spatula to ensure everything incorporated. Be careful not to over mix, stopping as soon as the flour mixture is completely blended into the donut batter. Over mixing batter will negatively affect the texture of the donuts.
Spray the donut pan with non-stick cooking spray.
Add a portion of the donut batter to a gallon size Ziploc or a piping bag. I do this by propping the bag up in a large glass and folding over the sides. Do not overfill the bag as the batter will end up flowing over the top.
Gently squeeze the batter into each cavity in the donut pan, filling about 2/3.
Bake until golden brown and a toothpick inserted into a donut comes out clean, about 20 minutes.
Let the donuts cool for ten minutes in the pan, then transfer to a wire rack. If want a simple powdered sugar coating, roll the warm donuts in the sugar and allow to cool.