Preheat oven to 400 degrees F. Place butter in a 10" cast iron skillet or a 9x13" baking dish and place in the oven while preheating.
Meanwhile, beat eggs in a medium bowl. Add in flour, milk and sugar and beat just until combined. DON'T overmix or the pancake will not puff up.
Remove skillet or dish from oven and pour in the batter. Sprinkle with blueberries then bake for 25-30 minutes or until puffed and the edges are golden. Serve immediately with lemon curd if desired.