How to Make It
In a bowl, whisk together flour, brown sugar, baking powder, salt, and cinnamon until well combined. In a separate bowl, whisk together eggs, milk, and vanilla. Add dry ingredients to wet ingredients and whisk until no lumps remain. Allow to rest for 15 minutes before using.
While batter is resting, heat 2 inches of vegetable oil in a Dutch oven or deep fryer to 375°F. Line a plate with paper towels; set aside.
Transfer batter to a pitcher. Making 1 funnel cake at a time, pour 1/3 cup batter into oil in a small steady stream, pouring mixture in circles that overlap, making one large circle roughly 6 inches wide. Fry for 2 to 3 minutes, flipping the funnel cake over halfway through frying using a slotted spatula, until evenly browned all over. Transfer to paper towel-lined plate to dry. Repeat with remaining batter.
Dust each funnel cake generously with powdered sugar and serve immediately.