Preheat oven to 425 degrees. In a bowl, combine the sugar and lemon zest. Toss the sliced strawberries and blueberries with 2-3 tablespoons of the lemon sugar and set aside.
Whisk eggs, milk, flour, vanilla, salt, and 1/2 teaspoon cinnamon in a medium bowl until smooth.
Melt 2 tablespoons butter in a 10 inch skillet, preferably cast iron, over medium heat allowing it to brown a little. Pour the batter into the skillet. Arrange 4-5 strawberries and some of the blueberries over the batter, then sprinkle with 1 - 2 teaspoons of the lemon sugar.
Place the skillet in the center of the oven and bake for 15 minutes or until the pancake is fully puffed and browned on top. Do not open the oven while cooking and cook for 12-15 minutes.
Serve with the remaining berries, the lemon sugar and the whipped cream. Serve with syrup if you like.