Adjust an oven rack to the lower-middle position and heat the oven to 375 degrees. Whisk the flour and salt in a medium bowl. Whisk the milk, egg, and vanilla in a small bowl. Make a well in the center of the flour mixture and pour the milk mixture in. Whisk until combined; a few small lumps may remain.
Melt the butter in a 12-inch ovenproof skillet over medium heat. Pour the batter into the center of the skillet and let it level itself. Scatter berries over the batter, leaving a 1-inch border around the edges. Sprinkle the sugar over the berries, again avoiding the 1-inch border.
Bake until the edges are puffed and deep golden brown, 50-60 minutes. Transfer to a serving plate and serve immediately.
Notes
Use any combination of berries that appeals to you for this recipe. I used blueberries. The original recipe calls for ¾ cup sugar; I reduced this amount to ½ cup and still found it to be a bit on the sweet side.
Recipe by Sprung At Last at https://sprungatlast.com/2013/10/waukau-berry-pancake/