Preheat your oven to 350°F (175°C) and line a loaf pan with parchment paper.
In a large mixing bowl, combine almond flour, whey protein isolate, ground flaxseed, salt, and baking powder. Mix well until all dry ingredients are evenly distributed.
In another bowl, whisk together the eggs, almond milk, olive oil, and apple cider vinegar. Gradually add the wet mixture to the dry ingredients, stirring until you have a smooth batter.
Pour the batter into the prepared loaf pan and smooth the top with a spatula. Bake in the preheated oven for 45-50 minutes, or until the top is golden brown and a toothpick inserted in the center comes out clean.
Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.