Mix the almond flour, coconut flour, sweetener, baking powder and lemon zest together in a small bowl. Add the egg, butter (or oil) and lemon juice to the dry ingredients mixing until well combined.
Grease the inside of 2 mugs/ramekins and evenly distribute the batter. Smooth out the tops of the batter.
Microwave for 2 minutes on high or until cakes have cooked inside but are still moist. Allow the cakes to sit on the bench for a few minutes as they will continue to cook out of the microwave oven.
If you wish to flip your mug cakes out of the mug onto a plate, you may need to cook them for a few seconds longer to ensure the batter has cooked all over. If flipping, leave cakes to cool before running a knife around the edges and tipping out onto a plate.
If pouring on the syrup you can poke holes with a skewer into the cake and pour the syrup onto the cakes, after sitting for about 5 minutes at room temperature. If you want to frost/ice the cakes, allow to cool before frosting to prevent the mixture from melting.
Lemon Syrup
In a small bowl mix the powdered erythritol, heavy cream, and lemon juice until smooth. Pour over lemon cakes when hot or cold. You can poke holes in your cakes with a skewer so it oozes into the cake more.
Notes
If you use a stevia or monkfruit blend you may want to use less sweetener as it is more concentrated in sweetness. If you reduce the amount of sweetener used you may have to add a bit more almond flour/almond meal to replace the dry ingredients in the batter.If you want more subtle lemon flavors, reduce the amount of lemon juice to suit your taste and omit or reduce the lemon zest if desired.Omit the lemon syrup and top simply with whipped cream, Greek yogurt or a low carb custard. Turn your mug cake out if pouring custard over it.For a paleo version use the EVOO-extra virgin olive oil instead of butter and your favorite paleo friendly sweetener such as coconut flour. Switch any heavy/pure cream in the recipe with coconut cream and top your mug cake with whipped coconut cream or coconut yogurt.Note that the recipe is based on Australian tablespoons (20 gms) that are larger than other tablespoon measures (15 gms). Click on US customary for the smaller tablespoon conversion.
SIMPLE VARIATIONS
Lemon Blueberry- add 10 fresh or frozen blueberries to the batterLemon Poppy Seed- add 1 teaspoon poppy seeds to the batterLemon Coconut- switch 1/2 of the coconut flour for 1 tablespoon of desiccated coconut