Preheat oven to 350ºF and grease 4, 8 ounce ramekins with butter or coconut oil and set them in an 8x8-inch baking dish. Bring a kettle full of water to a boil (you will use this for a hot water bath for baking later).
Beat together the butter, salt, and monk fruit until light and fluffy with a handheld or stand mixer. Add the egg yolks and beat until incorporated, light, and fluffy.
Stir in the lemon zest, almond flour, cream, lemon juice, and vanilla extract and mix until combined. Set aside.
Using the handheld or stand mixer, whip the egg whites to stiff peaks (the egg whites should hold their shape when the mixer is lifter without folding over).
Fold the whites completely into the batter that is set aside, being careful not to knock the air out.
Divide the batter among the ramekins. Transfer the baking dish containing the ramekins into the oven then fill the baking dish with boiling water until it reaches half way up the ramekins.
Bake for 45 minutes, or until there is only a slight wiggle when you gently shake a ramekin. Remove from the oven and cool for 10 minutes before enjoying.