Prepare The Batter: In a bowl, mix the almond flour, coconut flour, baking powder and erythritol together. Whisk well to remove lumps.
Add Wet Ingredients: Add eggs, melted butter, vanilla extract and heavy cream. Whisk together until the batter is smooth.
Bake the Cake: Pour the batter into a lightly greased 8-inch cake liner (it helps to crumble up the liner before using it to fit in nicely into your tin) and bake at 350°F (175°C) for 25–30 minutes, or until a toothpick inserted come out clean.
Make Caramel Sauce: Melt butter in a small saucepan over low heat, add allulose and stir till golden. Stir in heavy cream, vanilla and sea salt; cook until thickened.
Assemble the Cake: Cool for 15 minutes. Evenly pour the hot caramel sauce over it.
Serve: Cut and serve your buttery, moist Keto Caramel Cake with no guilt!