Fill a Dutch oven with about 3-4 inches of vegetable oil. Hook a candy thermometer on the side of your pot.

In a large bowl, whisk together the flour, baking powder, sugar, and salt.

In a smaller bowl, stir together the milk, egg yolks, vanilla, and lemon zest.

Pour the wet ingredients into the dry ingredients.

Use a spatula to combine the ingredients until a batter forms. 

In another medium glass or metal bowl, use a hand mixer to beat the egg whites on medium speed until stiff peaks form, and then gently fold the egg whites into the batter.

Cover the bowl with plastic wrap and allow it to rest for 15 minutes.

Meanwhile, line a baking sheet with a paper towel. Set aside.

Place your Dutch oven over medium-high heat and bring it up to 375 degrees.

Use a cookie scoop to drop the batter into the hot oil, 4 or 5 at a time.

Fry until they are a medium golden brown – about 3-4 minutes.

The beignets will flip over on their own as they cook.

Use a wire spider or slotted spoon to remove the beignet to drain on the paper towel-lined baking sheet.

Continue with the remaining batter.

While the beignets are still hot, lightly brush them with the butter and dust them with powdered sugar.

Serve immediately.