In a small glass measuring cup, or oven safe mug, combine melted butter, sweetener, egg, and gelatin. Stir well to combine. Add lemon extract, juice, and zest.
Add dry ingredients, stirring well. Be sure to scrape bottom and sides. If using a ramekin, grease it well. Place cake in microwave. Heat beginning at 60 seconds. Continue to heat as needed for 10 second intervals until just cooked. Remove and set aside.
Make glaze by combining ingredients.
Remove cake from mug or ramekin. Using a toothpick, poke holes in surface of cake.
Slowly pour glaze over surface of cake, letting it fall along the sides if desired.
