Grind the millet in a coffee grinder and place in a medium bowl with the baking powder, baking soda and salt. Whisk together.
Preheat the oven to 450F. Grease a 10-inch oven-proof pan with coconut oil and place it in the oven to warm up for 5 minutes.
Dissolve the buttermilk powder in 1 cup of water and add in a food processor. Add the ½ cup sweet potatoes and the egg. Blend until smooth.
Combine the wet and dry mixtures and mix together.
Using oven mitts, remove the pan from the oven (be careful and remember that it’s very HOT) and pour in the mixture.
Bake for 15-20 minutes, until the top is golden and the edges slightly browned.
Let cool for 10 minutes before cutting and serving.