Prepare a 12 inch Dutch Oven for cooking, wipe out, spray inside lightly with cooking oil.
Heat up about 25 coals for cooking (the recipe calls for 19, but I always heat up extras). This will take approximately 30 minutes. While the coals are heating up, prepare the cake. The coals will be white when ready.
Cream butter, oil and sugars together in a bowl. Beat until smooth.
Add eggs and beat until smooth and fluffy about 1 minute.
Add flour, soda, powder, salt and cinnamon. Pulse until the flour disappears and is mixed well with the butter mixture.
Leaving the mixer on low, add the buttermilk a little at a time until all of the buttermilk is added to the mixture in the bowl. Mix for one additional minute or until all ingredients are incorporated.
Create base layer by melting butter in the bottom of the Dutch Oven. Add the brown sugar and peaches and spread the peaches out into a single layer in the bottom of the Dutch oven.
Pour the cake mix over the peaches, place the lid on top of the Dutch Oven.
Place 12 hot coals on top of the Dutch Oven and 7 under the Dutch Oven.
Set a timer for 12 minutes. The cake will take 10-15 minutes to cook. When the cake has baked for 12 minutes, remove so the Dutch Oven is not over the coals. Continue baking with coals on top for a few more minutes, usually 3-4. Insert a toothpick in center to test cake. When toothpick inserted in center of cake comes out clean it is done.