In another bowl, whisk together the gluten-free flour, baking powder, cinnamon, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
In a small bowl, mix together the brown sugar and chopped nuts.
Pour half of the batter into the prepared pan, sprinkle with half of the brown sugar mixture, then add the remaining batter and top with the rest of the brown sugar mixture.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.
Allow to cool before serving.
Notes
For a dairy-free version, substitute the butter and milk with plant-based alternatives.
Store leftovers in an airtight container at room temperature for up to 3 days.