Preheat oven to 425 degrees.

Add eggs, milk, sugar, flour and salt to a blender and pulse just until batter is smooth. If using vanilla and lemon zest, add to batter and blend just to incorporate. Set blender pitcher aside.

Place butter in a 10-inch oven safe skillet. Place in a preheated oven until butter melts.

Open oven door and pour batter into skillet. Bake for 15-20 minutes (check after 15 minutes) until puffed and golden brown. Make sure the bottom is cooked through and not soggy or soft.

Remove skillet from oven and let cool until the puffing goes down before filling with lemon curd and blueberries or raspberries. Then sprinkle powdered sugar lightly overall. Cut into slices and serve.