Lightly grease a microwave-safe 10- to 12-ounce mug with butter or nonstick cooking spray.

In the mug, whisk together the Bob’s Red Mill 1-to-1 Baking Flour, sugar, baking powder, and salt. Add the milk, melted butter, vanilla, and lemon zest. Stir just until combined and no dry streaks remain.

Gently fold in the blueberries, being careful not to crush them.

Microwave on high for 60 to 90 seconds, or until the cake is puffed and the center is just set. Start checking at 60 seconds because microwave strength varies. Avoid overcooking, which can make the cake rubbery.

While the cake cooks, whisk together the powdered sugar, lemon juice, and lemon zest in a small bowl until smooth. If the glaze seems too thick, add a drop or two more lemon juice.

Let the cake cool for 1 to 2 minutes, then drizzle with the lemon glaze. Garnish with a few fresh blueberries and a little additional lemon zest, if desired. Serve warm.