Place butter in a 3 to 4-quart round or oval shallow-baking dish or casserole and set in a 425° oven.
Meanwhile, in a blender or food processor, whirl eggs at high speed for 1 minute.
With motor running, gradually pour in milk, then slowly add flour; continue to whirl for 30 more seconds or, in a bowl, beat eggs until blended; gradually beat in milk, then flour.
When butter is melted, remove pan from oven and quickly pour in batter.
Return pan to oven and bake for 20 to 25 minutes or until pancake is puffy and well browned.
Cut into wedges and serve immediately.
Offer powdered sugar and lemon wedges at the table.