Mix dry ingredients together in a small bowl or mug until combined.
Add in melted butter (or oil), milk and vanilla, and stir with a small whisk or fork until smooth.
Separate batter between 2 large baking cups (approx 6cm diameter).
Place first baking cup in the middle of the microwave and cook for 1 min on medium-high.
Remove the cupcake once cooked, and repeat the process with the other cupcake (the best way to obtain evenly risen cupcakes).