Preheat your oven to 350°F (175°C). Generously butter a 9-inch round baking dish, pie plate, or cast-iron skillet.

Peel and slice the bananas into 1/2-inch rounds and arrange them in a single layer in your prepared baking dish. Drizzle dark rum over the banana slices if using.

In a blender or food processor, combine the eggs, milk, cream, flour, sugar, vanilla, salt, and melted butter. Blend until smooth and frothy, about 30-45 seconds. Alternatively, whisk in a large bowl until well combined.

Pour the custard mixture over the banana slices. Tap the dish gently to remove air bubbles. Bake for 35-40 minutes until puffed, golden around the edges, and set in the center with a slight jiggle.

Remove from the oven and let cool for about 15 minutes. Dust with powdered sugar before serving. Enjoy warm or at room temperature for the best flavor.