Preheat oven to 350 degrees F. Lightly grease and flour a donut pan. (I recommend greasing and flouring the pan even if it is non-stick. It just makes it easier to remove the donuts).
Put the vegan buttery spread, brown sugar, and applesauce in a bowl and stir well.
Add the gluten free flour blend, oat flour, salt, baking powder, and spices to the bowl. Add the vinegar and water and stir until smooth.
Spoon the mixture into the donut pan, and smooth out with the back of the spoon.
In a small bowl, mix the brown sugar, vegan buttery spread, and oats. Sprinkle this streusel topping on the donut batter in the pan.
Bake at 350 degrees F for about 15 minutes. Let cool in the pan for 10-15 minutes, then overturn the pan and tap on the bottom to remove donuts.
Notes
Store leftover donuts in an airtight container. They should stay fresh for two days.