Step 1

Put oven rack in middle position and preheat oven to 450°F.

Step 2

Melt butter in a 9-inch oven-safe skillet over moderate heat, then transfer 2 tablespoons to a blender or food processor. Add apple slices to the skillet and cook, turning over once, until beginning to soften, 3 to 5 minutes. (They don’t need to caramelize, just soften.)

Step 3

While the apples are cooking, add milk, flour, eggs, granulated sugar, vanilla, and salt to butter in blender and blend until smooth. (Do do this step — I didn’t the first time around and the batter was really lumpy.)

Step 4

Pour batter over apple and transfer skillet to oven. Bake until pancake is puffed and golden, about 15 minutes. Dust with confectioners sugar and serve immediately.