Grease a microwave proof ramekin or mug with coconut oil, size 9 cm diameter and minimum 6 cm high to avoid overflow when baking. Set aside.
In a small bowl, beat together egg, oil or butter and sugar free crystal sweetener. Make sure your oil or butter is not too hot or it will 'cook' the egg and create lumps. Wait a few minutes after melting the oil before adding with egg.
Stir the almond flour in, baking soda and cinnamon. I recommend 1/2 teaspoon of ground cinnamon for a light cinnamon flavor, add up to 1 teaspoon if you are a cinnamon lover!
Transfer the batter into two ramekin and microwave 80-90 seconds individually. Time varies slightly depending on microwave power. The longer the dryer. The best is to start with 80 seconds, check and return for extra 10 seconds if you like.
Cool down 1 minute before adding fresh dairy-free coconut yogurt. Coconut yogurt is made of 2-ingredients, coconut cream and probiotics, don't use flavored coconut yogurt that will contain added sugar. Otherwise use plain Greek yogurt if you eat dairy.
In a small mixing bowl add peanut butter with coconut oil. Microwave 30 seconds to melt the coconut oil and easily combine both ingredients.
Stir in ground cinnamon, sweetener and use this mixture to drizzle on top of the yogurt.
Baking : if you don't have a microwave you can bake this cinnamon mug cake in the oven at 180C (350 F) for 12-15 minutes.Peanut butter swap : you can replace the peanut butter by any sort of nut butter like almond butter or sunflower seed butter or tahini. All these options are low carb keto friendly too.