Preheat oven to 375°.
Slice plums and set aside.
Combine oats, cinnamon, zest, baking powder, and sugar in a large bowl.
In a separate bowl, combine eggs, milk, honey, coconut oil, and vanilla extract.
Pour wet ingredients into dry and mix everything together by hand.
Line a 9x13" baking dish with coconut oil and then lay half of the sliced plums down on the bottom of the dish.
Pour the oatmeal mixture overtop, and then top with the rest of the plums.
Sprinkle with extra cinnamon and zest and place in the oven. Bake for 40-45 minutes, or until oats have set.
Remove from oven and wait a few minutes before cutting and serving.