Baked Apple Pancakes
Preheat oven to 425°F. Whisk milk, eggs, sugar, vanilla, salt, and cinnamon in large bowl until well blended. Add flour and whisk until batter is smooth. Place butter in 13x9-inch glass baking dish. Place dish in oven until butter melts, about 5 minutes. Remove dish from oven. Place apple slices in overlapping rows atop melted butter in baking dish. Return to oven and bake until apples begin to soften slightly and butter is bubbling and beginning to brown around edges of dish, about 10 minutes.
Pour batter over apples in dish and sprinkle with brown sugar. Bake pancake until puffed and brown, about 20 minutes. Sprinkle with powdered sugar, if desired. Serve warm.