Preheat your oven to 350 degrees F. Grease two 6-welled donut pans (if you only have one, you'll just have to reuse it once the first batch is baked). Set aside.
Make the donut base:
In a large microwave-safe bowl, melt the butter. Whisk in the buttermilk, sugar, egg, and vanilla until well-combined. In a separate bowl, whisk together dry ingredients - flour, cinnamon, salt, baking soda, and baking powder.
Pour the dry ingredients into the wet, and stir to combine with a large spoon or spatula. Stir until the ingredients are just combined, with no big patches of flour. Do not over mix - if you do, the donuts will be tough, and no one wants that.
Spoon the batter into the donut cavities, or pipe them in by filling a gallon-sized bag with the batter, then snipping off a corner for a makeshift pastry bag. Fill each cavity about 2/3 of the way full, or else your donuts won't have holes in the middle! The recipe yields 7 or 8 donuts depending on how full you make them (I got 7 once and 8 another time), so if you only have one donut pan, you'll have to bake the first 6 and then the other 1 or 2 afterwards.
Make the crumb topping:
In a small bowl, whisk together sugars, cinnamon, and flour. Cut the cold butter into the flour mixture with a fork, pastry cutter, or my favorite method, your fingertips. Stop when some bits of butter are pea-sized, and some of the mixture looks like coarse sand.
Arrange the diced peaches evenly over the batter in each donut cavity, making sure to press them lightly to adhere.
Distribute the crumb topping evenly over the peach donut batter, pressing to adhere. Make sure you press it down so it doesn't fall off during baking.
Bake donuts for 10-11 minutes, until lightly browned on the edges and tops (mine were done at 10). Set aside to cool for 2-3 minutes, then remove to a wire rack set over parchment paper or a baking sheet. Bake the remaining one to two donuts now if you only have one pan.
Dust the tops of each donut with a light coating of powdered sugar. Serve warm or at room temperature.
Donuts are best eaten the same day, although they will keep for up to two days, covered tightly and stored in the fridge. Just microwave for a few seconds to re-warm.Adapted from my Baked Apple Cider Donuts.
Find this and more delicious recipes at www.katiebirdbakes.com! Please rate and leave a comment on this recipe if you enjoyed it, and tag @katiebirdbakes on Instagram!