In a microwave-safe mug, combine the all-purpose flour, granulated sugar, baking powder, baking soda, cinnamon, and salt. Mix well until combined.
Add in the milk, vegetable oil, and vanilla extract. Stir until the batter is smooth and free of lumps.
In a small bowl, mix the brown sugar and ground cinnamon to create the cinnamon swirl topping.
Gently fold the cinnamon-sugar mixture into the batter, creating a few swirls, but not fully mixing it in.
Microwave the mug on high for 1 minute. Check to see if it has risen and is cooked through. If it’s still wet, microwave in 10-second bursts until done, but be careful not to overcook.
Once the cake is cooked, let it cool for a minute. If desired, drizzle with cream cheese frosting for added sweetness.
Notes
Enjoy the mug cake warm, topped with a sprinkle of powdered sugar or a scoop of vanilla ice cream on the side for an indulgent treat!