In a medium bowl, whisk together the flour, sugar, baking powder, salt, and cinnamon. Set aside.
In a separate bowl, combine the eggs, milk, vanilla, and melted butter.
Add the egg mixture to the flour mixture, stirring until combined.
Fold in the blueberries.
Fill a frying pan halfway with oil. Heat over medium heat until the oil reaches 375°F with a candy thermometer.
Slowly drop ¼ cup of batter into the oil and let fry until golden brown, about 2-4 minutes per side depending on the heat of your oil.
Flip and fry until the opposite side is golden brown. To test for doneness, insert a small knife (or toothpick) into the center. If there's still uncooked batter in the center, fry for a bit longer. Transfer to a paper towel-lined cooling rack and let cool. Repeat with the remaining batter being sure to check the temperature of the oil throughout the process.