To make mug cake: Add butter to a mug and microwave until melted, about 30 seconds.

Add sweetener, egg and coconut flour to the melted butter and mix to combine fully.

Microwave mug cake for two minutes and let sit for several minutes until cool.

To make strawberry filling: Add fresh/frozen strawberries to a microwave-safe container and microwave until slightly softened.

Add lemon juice and vanilla extract, and mash until desired consistency.

To make whipped cream: Add heavy whipping cream and sweetener to a small bowl and beat with a mixer until it becomes a whipped cream consistency.

To assemble: Cut mug cake into two or three slices.

Place first layer of mug cake on a plate and top with a layer of strawberry filling, followed by a scoop of whipped cream.

Repeat until all slices of mug cake are used up.