Preheat oven to 425° with a rack in center and another beneath it. In a blender, whirl eggs, milk, and salt to break up. Add flour and whirl until smooth; set aside.
Divide butter among 12 muffin cups (1/3-cup size). Bake on center rack in oven until butter melts and begins to brown, 2 to 3 minutes. Pour batter into cups and sprinkle with raspberries. Set on center rack and put a rimmed baking sheet beneath to catch any drips. Bake until dutch babies are very well-browned and puffed, 18 to 20 minutes.
Sift powdered sugar over dutch babies. Loosen from pan with a knife and spoon and serve immediately.