In a microwave-safe mug, whisk together the dry ingredients: flour, sugar, baking powder, and salt until well-blended.

Pour in the wet ingredients: milk, melted butter, and vanilla extract. Stir vigorously until the mixture is completely smooth.

Spoon cherry pie filling into the center of the batter without stirring. Gently press it down slightly.

Microwave the mug on high for 90 seconds. Check for doneness and continue in 10-second intervals if needed.

Carefully remove the mug from the microwave and let it cool for 1 minute before serving. Optionally, top with ice cream or powdered sugar.