preheat oven to 425°F. melt butter in a 12-inch ovenproof frying pan over high heat. add brown sugar & cinnamon, swirling to combine. add apple & cook until starting to soften, about 3 minutes

meanwhile, in a blender, whirl together eggs, salt, flour, & milk. pour egg mixture into pan & bake until puffed & brown, about 15 minutes. sprinkle with juice & powdered sugar