Preheat the oven to 325 F. Place the heavy cream in a small saucepan and heat until it is starting to gently simmer and bubbles form around the edge of the pan.
In the meantime, whisk together eggs, the sweetener, and the vanilla.
Add the egg mixture to the heated cream, whisking until it is all combined. Remove the custard from the heat and divide it between two oven-proof 4-oz ramekins.
Place the ramekins into an 8” x 8” glass baking pan and add boiling water around the edges until the water comes up the sides about 1”. Bake in the oven for about 60 minutes. The custard is ready when it jiggles together as one piece. It is not done if the outside and the inside of the custard are moving separately from each other when jiggled.
Chill the ramekins for about one hour, and then consume immediately or within one day.