Peel and core your apples (a tart apple like McIntosh or Granny Smith is best) then cut them into ¼-inch slices.
Spread the apple mixture evenly into the bottom of a greased 9x9-inch baking dish. A glass or ceramic baking dish works best for apple crumble.
In a new bowl, mix flour, oats, salt, cinnamon, baking powder and butter. Cut the butter into the oats and flour with a fork or use your fingers to combine the mixture; it’s done when it has a crumbly consistency.
Sprinkle the oat mixture evenly over the apple filling and bake the apple crumble until it’s hot, bubbling, and golden brown, about an hour and a half. Then, let your apple crumble cool slightly before serving.
Kristie Collado is The Daily Meal's Cook Editor. Follow her on Twitter @KColladoCook.