Preheat your oven to 375°F (190°C). Grease a donut pan.
In a mixing bowl, whisk together the flour, sugar, baking powder, cinnamon, and salt.
In another bowl, combine the milk, eggs, melted butter, and vanilla extract.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Spoon the batter into the prepared donut pan, filling each cavity about ¾ full.
Bake for 12-15 minutes, or until the donuts are golden brown and a toothpick inserted into the center comes out clean.
Let the donuts cool in the pan for a few minutes, then transfer to a wire rack to cool completely.