01 - In a large bowl, mix flour, sugar, yeast, and salt until evenly distributed.
02 - In a separate bowl, whisk together the warm milk, melted butter, eggs, and vanilla extract.
03 - Pour wet ingredients into dry ingredients and mix until a sticky dough forms.
04 - Knead the dough on a lightly floured surface for 5 to 8 minutes until smooth and elastic.
05 - Place dough in a greased bowl, cover, and let rise in a warm area until doubled in size, about 1 hour.
06 - Roll out dough to 1/2-inch thickness. Cut out donuts and holes using appropriate cutters approximately 3 inches and 1 inch in diameter.
07 - Arrange donuts and holes on a parchment-lined tray, cover, and allow to rise for 30 minutes.
08 - Heat vegetable oil in a deep pot to 350°F. Fry donuts 1 to 2 minutes per side until golden brown; fry holes for 1 minute, turning once.
09 - Remove donuts from oil and drain on a paper towel-lined rack to remove excess oil.
10 - Brush warm donuts with melted butter, then toss in mixture of sugar and cinnamon until evenly coated.
11 - Serve the cinnamon sugar-coated donuts warm for optimal flavor.