Combine berries and sugar in a small bowl and set aside. Place 4 (6 to 7 inch) individual gratin dishes on a baking sheet. Place 1 teaspoons of butter in each gratin dish and set aside.
Place the eggs in the bowl of an electric mixer fitted with the whisk attachment and beat on medium speed until combined. Add the milk and mix. Slowly add the flour, vanilla, lemon zest, 2 T of melted butter, and the salt and mix just until smooth. Whisk by hand if the batter is still lumpy.
Place the gratin dishes in the oven for three minutes, until the butter is hot and bubbly. Make sure the butter covers the bottom of each dish. Divide the batter equally among the four dishes and bake 12-14 minutes, until puffed and lightly browned. Divide the berries among the dishes and sprinkle with powdered sugar. Add syrup if you wish. Serve hot!