Preheat your oven to 175°C (350°F). Grease and flour a 23 x 13 cm (9 x 5 inch) loaf pan, or line it with parchment paper.

Mash the very ripe bananas in a large bowl until mostly smooth, leaving a few small lumps for added texture.

Whisk together the melted and cooled unsalted butter, granulated sugar, light brown sugar, eggs, and alcohol-free vanilla extract until smooth.

In a separate bowl, whisk together the all-purpose flour, baking soda, fine sea salt, ground cinnamon, and ground nutmeg until mixed.

Gently mix the dry ingredients into the wet ingredients using a spatula, being careful not to overmix.

Layer half of the batter into the prepared loaf pan. Dollop half of the dulce de leche over and swirl it in.

Repeat with the remaining batter and dulce de leche, swirling again.

Bake for 60-70 minutes, or until a wooden skewer inserted into the center comes out clean.

Cool the banana bread in the pan for 15 minutes before lifting it out onto a wire rack to cool completely.

Slice once cool and drizzle any remaining dulce de leche over slices, finishing with a dusting of ground cinnamon.