Preheat the oven to 425°F (220°C). Place your baking dish or skillet in the oven while it's preheating (this will help the batter puff up).
Make the batter: If you have a high-speed blender – just add all the ingredients and blend until the batter is smooth, about 30 seconds.
If you have a hand/immersion blender or prefer to whisk the batter by hand: first add eggs, flour, sugar, vanilla, and salt to a large bowl. Mix or whisk until smooth. Add the milk and continue mixing until smooth. Set aside.
7 large eggs, 1 1/8 cups (145g) flour, 3 tablespoons sugar, 2 teaspoons vanilla extract, pinch of salt, 1 1/8 cups (270g) milk
Prepare the apples: peel apples, cut into quarters, remove the cores, and cut into slices.
3 medium apples or 2 large
Cook apples: heat the butter in a large frying pan over high heat, add apples, and spread them evenly in the pan, don't stir for about 2 minutes, letting the apples brown. Start stirring, add sugar, vanilla, lemon juice, and cinnamon. Cook for a couple of minutes until the apples are softened and slightly browned.
2 tablespoons butter, 2 teaspoons vanilla extract, 2 tablespoons sugar, 1 teaspoon lemon juice, 1/2 teaspoon cinnamon
When the oven is heated up, take the baking dish (or baking dishes) out of the oven and add the butter. Melt the butter moving it all around the baking dish, also on the edges, it should melt quickly.
2 tablespoons butter
When the butter is melted, add the cooked apples (if using two dishes, divide them evenly between them), pour in the batter.
Place the baking dish again in the oven and bake for about 15 minutes or until golden and puffed up.
Take out of the oven, cut into servings, and serve immediately.
Dutch baby pancake puffs up in the oven but quickly deflates when taken out of the oven, this is normal.
Enjoy!