Heat oven to 350 F. Butter an 8-inch square baking dish.
In a bowl, combine oats, pecans, baking powder, cinnamon, cardamom and sea salt. Set aside.
In another bowl, whisk together milk, eggs, maple syrup and melted butter. Set aside.
Spread sliced bananas, cranberries and ⅔ of the blueberries across bottom of prepared baking dish.
Sprinkle oat mixture on top of fruit. Pour milk mixture over all. Sprinkle remaining blueberries across the top.
Bake 35-40 minutes. Cool 10 minutes, then cut into squares to serve.
Can be made ahead, kept refrigerated and then heated in the microwave for 1-2 minutes.