Preheat your oven to 350°F (175°C). Lightly grease a 9x9-inch baking pan or line with parchment paper.

In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, and salt.

In another bowl, whisk the egg, maple syrup, brown sugar, yogurt, milk, vanilla extract, and melted butter until smooth.

Combine wet and dry ingredients and stir until just incorporated.

Pour the batter into the prepared pan and smooth the top.

Bake for 18–22 minutes, or until a toothpick inserted in the center comes out clean.

Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

To make the glaze, whisk powdered sugar, maple syrup, and milk until smooth and pourable.

Drizzle the glaze over the cooled donut bars. Allow to set before slicing and serving.