Preheat the oven: Set to 350°F (175°C). Line a 8.5×4.5-inch loaf pan with parchment paper, leaving overhang for easy lifting.
Lightly grease the sides.
Mix dry ingredients: In a large bowl, whisk almond flour, coconut flour, baking powder, and salt until no clumps remain. This prevents dense pockets later.
Whisk wet ingredients: In a separate bowl, beat the eggs well. Add almond milk, olive oil, vinegar, and optional sweetener.
Whisk until smooth.
Combine: Pour wet mixture into dry. Stir with a spatula until just combined. The batter should be thick but spreadable, not runny.
Rest briefly: Let the batter sit for 2–3 minutes.
Coconut flour hydrates and helps set the structure.
Fill the pan: Scrape the batter into the prepared pan. Smooth the top with a spatula. Sprinkle optional seeds on top.
Bake: Place on the middle rack and bake 35–45 minutes.
The top should be golden, and a toothpick inserted in the center should come out clean or with a few dry crumbs.
Tent if needed: If the top browns too quickly around 30 minutes, loosely tent with foil and continue baking until done.
Cool in pan: Let the loaf rest in the pan for 10–15 minutes. This helps the crumb set and reduces breakage.
Cool fully: Lift out using the parchment and cool on a rack for at least 1 hour before slicing. Use a sharp serrated knife for neat slices.