Whisk flour, salt, baking powder and sugar together in a medium bowl. Set aside.
Whisk milk, eggs and vanilla together in a large bowl. Add the dry ingredients and whisk until completely smooth.
Pour the oil into a 12-inch dutch oven or deep skillet. Heat the oil over medium heat until the temperature reaches 350 degrees.
Meanwhile, transfer the batter to a plastic ziploc bag. Cut a tiny hole in the corner of the bag that is about ⅛-¼ inch in diameter.
Drizzle the batter into the hot oil in a figure eight motion, continuing until you have a bird’s nest-like circle that is 3 or 4 inches in diameter. Repeat so that you are cooking two cakes at a time.
Fry until golden brown, about 45 seconds to 1 minute on each side. Transfer to a paper towel-lined plate to drain. Repeat with remaining batter. Dust the funnel cakes with powdered sugar and serve immediately.
Notes
It's important to use a figure 8 motion when drizzling the batter into the hot oil. If you just try to go in a circle, the drizzled batter won't stick together, and it will scatter throughout the pan and not form into a cake. It might take you a couple of cakes to get the hang of it so be patient!