In a large mixing bowl, add and whisk the flour, baking powder, salt, and cinnamon. Set aside.
In another large mixing bowl, with an electric mixer on medium, cream together the granulated sugar and eggs until thickened. Add in the maple syrup, vanilla, and melted butter until combined.
Add about ⅓ of the dry ingredients to the egg mixture and fold with a spatula until incorporated. Pour in ½ of the half and half until combined. Repeat the process alternating dry and wet ingredients until all is combined. Do not over mix. Place plastic wrap on the dough in the bowl and refrigerate for 1 hour.
Pour oil into pan and heat until 365°. Use a thermometer for accuracy.
Remove dough from fridge and transfer to a lightly floured surface. Roll out dough with rolling pin until it is about ½ inch thick.
Using a 3 inch round cutter, cut up donuts until no more dough remains. Place on a baking sheet with parchment paper.
Once oil has reached the desired temperature, fry about 3 donuts at a time. Fry on one side for about 1 minute and flip with tongs to fry other side for an additional minute. Allow donuts to cool on paper towel lined wire racks.