Preheat the oven to 425°F. In a medium bowl, whisk together the eggs, milk, flour, granulated sugar, nutmeg and salt until combined. The mixture will still have some lumps and that’s a good thing.
In a 9-inch cast-iron skillet, melt the butter over medium heat. When the butter has melted, lower the heat slightly and allow the butter to brown – you’ll see the golden flecks in it when it has. Watch carefully – it’s hard to miss against the cast-iron and you don’t want it blackened. That has its merits, but not here.
Carefully pour the pancake batter into the skillet and transfer it to the oven. Bake until the pancake is golden brown around the edges and puffed, 15-20 minutes.
Working quickly, take the skillet out of the oven and, using a fine-mesh sieve, shake the confectioner’ sugar over the pancake.
Splash the lemon juice over the pancake, cut into wedges and serve immediately.