For the crust: Combine melted butter with almond flour, coconut flour, and erythritol. Transfer the dough into a 9x9 pan lined with parchment paper. Refrigerate until set.
For the caramel layer: Mix melted butter with sugar-free and keto-friendly maple syrup. Add cinnamon and vanilla. You might want to microwave for 30 seconds to one minute so the mixture can be mixed easily and smoothly.
Pour the caramel layer over the crust. Let it cool on the counter before placing it in the freezer. When the caramel is completely set, we prepare the chocolate layer.
For the chocolate layer: melt dark chocolate and butter in a microwave or double-boiler. Stir until the chocolate is completely melted then pour the chocolate over the caramel layer. Use a spatula to flatten it.
Refrigerate at least one hour before cutting. Cut into 10 bars and serve.