Preheat the oven to 350 degrees F (175 degrees C). Grease a muffin tin or line with paper muffin liners.

Mix sweetener, almond flour, coconut flour, poppy seeds, lemon zest, baking powder, salt, and xanthan gum together in a bowl.

Beat eggs in a bowl with an electric mixer on high speed until fluffy, about 2 minutes. Beat in butter, sour cream, and vanilla. Add sweetener mixture. Stir in cream slowly until batter is thick and smooth. Pour into the prepared muffin tin.

Bake in the preheated oven until tops are golden, 15 to 20 minutes.