In a microwave-safe mug, add the self-raising flour (or all-purpose flour with baking powder).

Add sugar and salt to the flour. Mix well.

Add the mashed avocado, milk, and vanilla extract to the dry mixture. Stir until everything is well combined.

Place the mug in the microwave and cook for about 90 seconds. If the top is still a bit wet, microwave for an additional 30 seconds, depending on your microwave's power.

Let the cake cool for a minute before enjoying it straight from the mug.