Start by lightly greasing a microwave-safe mug with a few drops of neutral oil like canola or vegetable oil. This ensures your cake slides right out without sticking.

Next, add the melted butter, milk, and vanilla extract into the same mug. Use a fork to mix everything together until it's smooth and combined, giving your cake that moist texture.

Now, stir in the granulated sugar, making sure it blends nicely with the wet ingredients. The sugar will dissolve and create the perfect sweetness, just the right amount for indulging.

Time to add the dry ingredients! Mix in the flour, baking powder, and a pinch of salt. Stir well until the batter is smooth and lump-free, this will help your cake rise perfectly.

Pop the mug in the microwave and heat it on high for about 1 minute and 30 seconds. Microwaves can vary, so make sure to watch it closely while it cooks. Your cake should rise and set on top. If it needs more time, add a few extra seconds, but don't overdo it or it could become dry.

Once it's done, let it cool for a minute or so. If you're in the mood, top it off with sprinkles or any other fun topping you like. 

Finally, grab a spoon and enjoy your warm, delicious treat!