Preheat the oven to 350°F and line an 8x8 baking pan with parchment paper.
In a small mixing bowl, whisk together the milk, applesauce, eggs, maple syrup, and vanilla.
In a separate bowl, combine together the rolled oats, baking powder, salt, and cinnamon.
Once the dry ingredients are well distributed, pour in the wet mixture and add in the diced apples. Fold the apples in until well combined and evenly distributed.
Pour into the prepared baking pan and bake 40m, until set and lightly golden. Cool slightly before slicing and dust with powdered sugar.
Notes
Use rolled oats, not quick cooking or steel cut oats. The texture and the taste will change how it bakes.Give the oatmeal a chance to cool a little before slicing and serving.Use enough liquid to keep the baked oatmeal moist when it's finished baking, and when reheated. Sometimes baked oatmeal can dry out if there is not enough moisture.