Preheat oven to 350* and spray donut pans with non stick spray
Combine flour, baking powder and salt.
In a separate bowl, whisk together the brown sugar of choice and egg. Add milk, yogurt and vanilla and continue whisking until smooth.
Slowly add the wet ingredients to the dry ingredients and mix until just combined, you don't want to overmix this batter.
My favorite way to get the batter into the donut pan is to put the batter into a ziplock bag or pastry piping bag, snip the corner and pipe the batter into the pans. You will see why when you do it - I've tried spooning the mix into the pans and it's always a mess.
Bake donuts at 350* F for 8-10 minutes until lightly golden on the tops and are fully cooked in the middle
Melt the butter in a shallow bowl or plate. Make the cinnamon sugar mixture.
Remove the donuts from the pans and allow them to rest for a minute or two on a baking rack
Dip each donut in the butter and then into the cinnamon sugar mixture. You can do just the tops or both sides - your choice!
These pair wonderfully with a hot cup of coffee - serve them warm and enjoy - they are heavenly!