Step 1

Preheat oven to 350°F (175°C).

Step 2

Arrange the sliced apples into a 9x13-inch baking dish. Add the sugars, flour and cinnamon over the apple slices. Pour in the water and mix everything through until apples are evenly coated.

Step 3

In a bowl, combine the oats, flour, sugars, cinnamon, salt, baking powder and melted butter. Mix well using a metal spoon or your fingertips, until the butter has soaked through the dry ingredients (about one minute of mixing or less). Sprinkle evenly over the apple filling.

Step 4

Bake in preheated oven for 40 - 45 minutes, or until the crumb is golden and crisp and the apples are cooked to your liking.