Preheat the oven to 400 F. Grease a 9x13" baking pan lightly and set it aside. In a large bowl, whisk together the flour, sugar and salt. Then add the milk and vanilla. Next, whisk in each egg one at a time, whisking to combine for each one.

While the German pancake is baking, start preparing the apples. Heat the 2 tbsp. of butter in a large skillet over medium heat. Place the apple slices into a large bowl and toss them in the sugars and cinnamon. Then pour them into the skillet. Cook, stirring around often, for 5-7 minutes, until the apples have softened and the sugars have caramelized slightly.

Slice the pancake into 6 equal sized squares and serve with the apple slices atop it.