3 medium sweet, crisp apples, such as Honeycrisp (about 1 pound), peeled, cored, quartered and cut into 1/2-inch chunks
3 tablespoons granulated sugar
Confectioners' sugar, for dusting, optional
Preheat the oven to 400 degrees Fahrenheit. In a blender, combine the milk and eggs until fully combined. Blend in the flour, vanilla, cinnamon, 1/2 teaspoon salt, and lemon zest for another 15 seconds, scraping down the sides as needed. Refrigerate the blender jar while you cook the apples.
In a 10-inch nonstick oven-safe skillet, melt the butter over medium heat. Sprinkle the granulated sugar on top of the apples. Reduce the heat to medium-low and cook the apples, stirring occasionally, for 20 to 25 minutes, or until golden brown and softened. Arrange the apples in the skillet in an equal layer. After recombining the components in the batter, pour it over the apples.
Bake for 25 to 30 minutes, or until the pancake is golden and firm in the center and the sides have risen about 1 1/2 inch. Serve immediately from the skillet or transfer to a platter with a big spatula. Confectioners' sugar is sprinkled on top.