Make the caramel sauce according to the directions, but leave out the additional water in Step 4. Let it cool completely before proceeding.
Preheat the oven to 350F and lightly grease 4 small (4 ounce) ramekins.
In a large bowl, whisk together the pumpkin puree, melted butter, eggs, and vanilla extract. Stir in the sweetener, almond flour, and pumpkin pie spice until well combined.
Divide about ⅔ of the batter between the ramekins to cover the bottom of each. Use a spoon to make a well in the batter (you want some batter to cover the bottom of the ramekin but raised on the sides).
Spoon 1 tablespoon of caramel sauce into each well. Use the remaining batter to cover the caramel in each ramekin.
Bake 20 to 25 minutes, until the cakes are golden brown and the tops are just barely firm to the touch. The caramel sauce may be bubbling up a bit through the top.
Remove and let cool 10 minutes before serving in the ramekins (these will not stand up to be flipped out of the ramekins).
Top with keto vanilla ice cream, if desired, and the remaining caramel sauce. If the sauce has thickened considerably, add a tablespoon of water and re-warm gently in the pan.