Preheat the oven to 375 degrees F.
In a large bowl with electric mixer, beat the butter and sugar until well combined, about 2 minutes.
Add the maple syrup, egg, and vanilla extract, beating until combined. Scrape down the edges of the bowl as needed.
Add the baking powder, salt, and baking soda, and mix well to combine.
In a small bowl, whisk together the milk and sour cream until smooth.
Add one cup of flour, mixing until combined, followed by the sour cream/milk mixture.
Lastly, add the remaining cup of flour, mixing until just combined.
Divide the batter between 10 muffin cups, filling each cup ¾ full.
Bake in the preheated oven for 15-17 minutes, until slightly golden around the edges and no longer sticky on the top. Cool for 10 minutes.
Combine sugar and cinnamon in a small bowl.
Remove muffins from pan and place on cooling rack.
Brush each muffin with butter and then dip in cinnamon sugar mixture.
Serve and enjoy!