Preheat oven to 350. Spray a 9x13 baking pan with cooking spray.
Mix together all the cake ingredients. Spread in the prepared pan. This is a VERY thick batter.
Mix together the filling ingredients. Spread on top of the cake batter.
Bake at 350 for 40 min or until the cake is firm to the touch. A toothpick inserted in the center will come out with a few moist crumbs when it is done.
Nutrition: this cake has 18 large pieces. There are 4.3 NET carbs per piece. The recipe can be halved to fit an 8 x 8 pan and make 9 pieces.If you would like an even lower carb option you can make this keto apple cake with jicama instead by using the method I use in my Keto Apple Crisp.Brown Sugar Sweetener: To easily make your own mix 1 teaspoon of molasses into 1 cup of a 1:1 sweetener. Or ½ cup of a 2:1 sweetener such as Gentle Sweet or my sweetener.Apples: If you just want this to be sugar free and aren't counting carbs feel free to use 3-4 cups of chopped apples.Substitutions: Swap the sour cream for Greek yogurt or coconut cream. Feel free to use any firm apples that you like.To Reheat: If you prefer the cake to be warm, go ahead and heat it in the microwave for a few seconds. Start with 10 seconds and continue to heat as needed.To Freeze: Store the cake in a sealed container in the freezer for up to 2 months. You can thaw it in the fridge overnight before serving.Notes on Sweeteners: