Cover oatmeal in warm, filtered water. Add 1Tbs apple cider vinegar. Let it soak for 8-12 hours.
After soaking period, drain all water and let oatmeal drip dry in a collander while you gather other ingredients and get started with the recipe.
Place cast iron in the skillet and preheat oven to 350. Adding the skillet to the oven will allow it to get nice and hot.
Using a mixer blend together the soaked and drained oatmeal with the rest of the ingredients.
Carefully remove HOT cast iron pan from oven, add 2Tbs butter and coat the pan well. Then pour the oatmeal mixture into the pan. Place back into the oven.
Bake about 45 minutes or until center is set and oatmeal bake is slightly golden brown.