In a bowl, mix together the rolled oats, baking powder, cinnamon, salt, brown sugar, and zest from 1 lemon (you can use less zest if you don't want it to be as lemony).
In a separate bowl, mix together the milk, egg, and lemon juice from 1/2 of the zested lemon (you can add more or less lemon juice to your preference).
Combine and mix together the wet and dry ingredients and let it rest for 10 minutes.
While the oatmeal rests, prepare the berries. You can use any berries you want here, I did blueberries, strawberries, and blackberries. You want 1/2 cup of diced berries and 1/2 cup of sliced berries.
When the mixture is ready, spray an air fryer safe pan with non-stick spray oil.
Place the diced berries on the bottom, then pour the combined oatmeal mixture in.
Add the sliced berries on top. Then, sprinkle on almonds and nutmeg.
Cook in the air fryer at 300°F/150°C for 12 minutes. Check on the oatmeal after 10 minutes, if its done then remove from the air fryer basket.
Optional serving suggestion: enjoy with Greek yogurt on top!