Preheat your oven to 350°F (175°C) and grease an 8x8 inch baking dish.

Prepare your flax egg by mixing 1 tablespoon of flaxseed meal with 3 tablespoons of water if using a vegan option.

In a large mixing bowl, combine all dry ingredients: rolled oats, protein powder, baking powder, baking soda, salt, ground cinnamon, and nutmeg.

In another bowl, whisk together the wet ingredients: applesauce, almond milk, egg (or flax egg), vanilla extract, and maple syrup until smooth.

Gently combine the wet and dry mixtures, stirring until just incorporated.

Fold in the diced apples evenly into the batter.

Pour the batter into the greased baking dish and sprinkle with optional toppings. Bake for 30-40 minutes, or until a toothpick comes out clean.

Let it cool for 10-15 minutes before cutting into squares.

Serve warm, optionally topped with Greek yogurt or maple syrup.

Store leftovers in an airtight container in the fridge for up to 3-4 days or freeze for longer storage.