Step 1: Preheat your oven to 375°F (190°C). Line a standard loaf pan (8.5 x 4.5 inches) with parchment paper, leaving an overhang on the sides for easy removal.
Step 2: In a large mixing bowl, combine the almond flour, coconut flour, psyllium husk powder, baking powder, and salt. Whisk well to ensure all dry ingredients are evenly distributed.
Step 3: In a separate small bowl, combine the warm water, apple cider vinegar, and olive oil. Stir briefly.
Step 4: Gradually pour the wet ingredients into the dry ingredients. Stir vigorously with a spoon or spatula until a thick dough forms. Let the dough rest for 5-10 minutes; it will thicken further as the psyllium husk absorbs moisture.
Step 5: Spoon the dough into the prepared loaf pan. Use a wet spatula or the back of a wet spoon to smooth the top and gently shape the loaf.
Step 6: Bake for 45-50 minutes, or until the crust is golden brown and a toothpick inserted into the center comes out clean. If the top browns too quickly, you can loosely tent it with foil.
Step 7: Remove the loaf from the oven and let it cool in the pan for at least 10-15 minutes. Then, using the parchment paper overhang, carefully lift the bread onto a wire rack to cool completely before slicing. This is crucial for the bread to set and prevent crumbling.