Preheat your oven to 350 °F (176 °C). Line an 8½ × 4½-inch loaf pan with parchment paper, letting the ends hang over two sides for easy lifting.
In a large bowl, whisk together the almond flour, coconut flour, baking powder, cinnamon and sea salt until evenly distributed. The dry mix should feel light, slightly sandy.
In a separate mixing bowl, beat the softened butter and sweetener with an electric mixer until the mixture becomes pale, fluffy and a little airy (about 1-2 minutes). At this stage you’ll smell a buttery, sweet aroma rising.
Add the eggs one at a time, beating until each is incorporated. Then pour in the almond milk and banana extract, mixing until the batter looks glossy and smooth. Pause for a moment to inhale the banana extract’s fragrance — it gives that real banana-bread memory.
With the mixer on medium speed, gradually add in the dry flour mixture. The batter will thicken and pull away from the sides slightly. Fold in ¾ cup of the chopped walnuts by hand so you get small bits and crunchy texture.
Transfer the batter into the prepared loaf pan, smoothing the top with an offset spatula. Sprinkle the remaining ¼ cup of walnuts over the surface and press them lightly so they peek out and will brown on top.
Bake for about 30–35 minutes until the top is golden brown. Then cover loosely with foil and bake an additional 15–20 minutes until a toothpick inserted into the center comes out clean (you want that tender moist center without a raw spot).
Once baked, remove from the oven and let the loaf cool in the pan for 10 minutes, then lift it out using the parchment tail and place on a wire rack. Let it cool fully (about 30 minutes) before slicing. The aroma will deepen as it cools and the knife will slide through easily — if you slice too early it may still be a little unstable.
