Preheat your oven to 350°F (175°C).

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, brown sugar, baking powder, and salt until well combined.

Add the melted unsalted butter, milk, and vanilla extract to the dry ingredients. Stir gently until just combined.

Grease a 9x13 inch baking dish with non-stick cooking spray or butter.

Pour the prepared batter into the greased baking dish, spreading it evenly across the bottom.

Carefully slice ripe bananas and arrange them evenly over the batter.

In a small bowl, mix together ground cinnamon and nutmeg (if using), then sprinkle this over the sliced bananas.

Place the baking dish in the preheated oven and bake for approximately 45-50 minutes.

Once baked, remove from the oven and let it cool slightly before serving.