Wash and cut off the ends of 2 bananas, place them in a plastic bag, and freeze for a minimum of 8 hours until hard. Defrost at room temperature or overnight in the refrigerator, and they will be ready to use.
Preheat the oven to 190°C/375°F and place a rack in the center.
Puree the dark-spotted bananas in a food processor, including their skins, until smooth and the peels are barely noticeable.
Grease an 8x4-inch / 20x10-cm loaf tin with a small piece of butter, making sure to coat it well. Toss in 2 tablespoons of flour and shake the pan to coat the bottom and sides, then knock out the excess.
Melt the butter over low heat and set it aside to cool.
In a skillet, toast the anise seeds, pepitas, and walnuts separately for about 3 minutes each to bring out their earthy flavor. Set them aside to cool.
In a mixing bowl, combine the flour, salt, baking soda, 2 tablespoons of nigella seeds, ½ cup of pepitas, the anise seeds, and the walnuts. Stir well to combine.
Transfer the pureed bananas to a large bowl, then add the granulated sugar, melted butter, eggs (one at a time), and vanilla extract. Mix well to combine, scraping down the sides of the bowl. Add the flour mixture and mix just until all ingredients are incorporated.
Scrape the batter into the prepared loaf tin and smooth the top with a rubber spatula.
Mix together the remaining pepitas, nigella seeds, and turbinado sugar, then sprinkle the mixture evenly over the top of the batter. Bake for 1 hour 15 minutes, or until a toothpick inserted into the center of the bread comes out clean.
Remove the bread from the oven and place the tin on a wire rack. Let it cool in the tin for 10 minutes. Turn it out onto the rack, then turn it right side up. Serve warm, at room temperature, or even straight out of the fridge. How scrumptious