Place butter in a 9 by 13-inch pan and put in the preheating oven to melt the butter. When butter is completely melted, remove the pan from the oven and set aside.
Peel, core, and thinly slice apples. In a large bowl, mix apples with 1/4 cup of the flour, brown sugar, and cinnamon.
In another large bowl, whisk the remaining 1 1/2 cups flour with granulated sugar, salt and baking powder. Slowly add the milk, whisking as you go. Add vanilla extract and whisk until smooth.
Pour the batter into the baking dish over the melted butter, and then add the apples in an even layer over the top of the batter.
Bake for 50-55 minutes, or until the top is turning golden brown. Serve warm with a scoop of vanilla ice cream.
