Melt the butter: Place the butter in a microwave-safe ramekin and heat for 15-20 seconds or until melted.
Mix the batter: Add the almond flour, baking powder, salt, and egg to the ramekin. Whisk until smooth and fully combined.
Cook: Microwave for 90 seconds (or bake at 350°F/175°C for 12 minutes) until firm and springy to touch.
Slice and toast: Cool 2 minutes, slice in half If you like, toast it for some extra crunchiness.
Serving: Enjoy warm with butter or sugar free jam, or use as a sandwich base.