01 - Preheat the oven to 350°F. Grease an 8-inch square baking dish or similar casserole.
02 - In a large skillet, melt 2 tbsp butter over medium heat. Add the sliced bananas, granulated sugar, brown sugar, cinnamon, nutmeg, vanilla extract, lemon juice, and pinch of salt. Cook for 3–5 minutes, stirring gently, until the bananas are slightly softened and the mixture is saucy. Remove from heat and spread evenly in the prepared baking dish.
03 - For the topping, whisk together the flour, granulated sugar, baking powder, and salt in a bowl. Add in the milk, melted butter, and vanilla extract. Stir until just combined (do not overmix).
04 - Spoon the batter in dollops over the banana mixture. Use a spatula to gently spread, leaving some areas exposed for a rustic finish.
05 - Bake for 35–40 minutes, or until the topping is golden brown and a toothpick inserted in the topping comes out clean.
06 - Let cool for 10–15 minutes. Serve warm, optionally topped with vanilla ice cream or whipped cream.