Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and set aside.
In a mixing bowl, combine almond flour, coconut flour, 1 cup erythritol, baking powder, and salt for the cake.
Stir in the melted butter, eggs, almond milk, and vanilla extract until well combined.
Pour the batter into the prepared cake pan, spreading it evenly.
In a small bowl, mix together the chopped pecans, 1/4 cup erythritol, and ground cinnamon for the topping.
Sprinkle the pecan topping evenly over the cake batter.
Bake for 35 minutes, or until a toothpick inserted into the center of the cake comes out clean.
While the cake is baking, make the caramel sauce. In a saucepan over medium heat, melt 1/2 cup butter.
Add heavy cream, 1/2 cup erythritol, vanilla extract, and a pinch of salt. Whisk continuously for 5-7 minutes until the sauce thickens.
Once the cake is done, allow it to cool for 10 minutes, then drizzle the warm caramel sauce over the top of the cake.
Let the cake set for an additional 15 minutes before slicing and serving.