Preheat oven to 425 degrees. Put butter in 10-inch ovenproof frypan — a cast iron skillet is ideal. Melt butter in oven or on stove top. With a whisk or a blender, mix eggs until light and pale. Add milk and blend with vanilla, flour and salt. Add melted butter and mix lightly. Pour batter into greased skillet and bake until pancake is puffed and lightly browned, about 15-20 minutes. Sprinkle with powdered sugar, slice and serve. After puffed pancake comes out of the oven, it sinks in the center, into which you can add strawberies, blueberries, peaches or other fruit. This serves 2-4, depending on appetite.