Heat the oven to 425 degrees F. Combine the eggs, flour, cream, maple syrup, and salt in a blender. Blend on high to combine well. Melt the butter in an 8-inch (measured across the top of the pan) heavy-duty ovenproof nonstick skillet (such as an omelet pan) over medium heat. Add the apple slices and saute until soft and slightly browned, 5 to 7 minutes. Whiz the batter in the blender again until frothy, about 30 seconds. Pour the batter into the skillet (coax a few apples back to the center of the pan with a heatproof spatula), let the skillet sit for just a few seconds, and transfer it to the oven. Bake until the pancake is puffed, golden, and set, 12 to 15 minutes. Remove the skillet and let the pancake cool for a few minutes in the pan (it will deflate). Slide a flexible spatula or two under it and transfer to a cutting board. Sprinkle generously with cinnamon sugar or confectioners' sugar and a little cinnamon, cut into wedges, and serve warm.