Place a 9- to 10-inch cast-iron skillet in the bottom third of the oven and preheat to 425 degrees . In a small glass measuring cup, heat the milk in the microwave for 30 seconds at full power. Using a blender, mix the milk, eggs, 2 tablespoons granulated sugar and the salt briefly at low speed until combined. Add the flour and blend until just incorporated.
Add 2 tablespoons butter to the hot skillet to melt, then pour in the batter. Return the skillet to the oven and bake until the pancake is puffed and golden, about 20 minutes.
Meanwhile, in a medium skillet, combine the remaining 2 tablespoons each granulated sugar and butter, the peaches and lemon juice and cook over medium high heat until the juices are syrupy, about 5 minutes; remove from the heat. Dust the hot pancake immediately with the confectioners sugar, cut into 4 wedges and serve with the warm peaches.