Preheat the oven to 350°F (175°C).
Grease or line an 8x4-inch loaf pan with parchment paper.
Mix almond flour, flaxseed, baking powder, and salt in a large bowl.
In another bowl, whisk eggs until frothy.
Add melted butter, almond milk, vinegar, and vanilla to the eggs.
Pour the wet mixture into the dry ingredients.
Stir until a thick batter forms.
Transfer the batter into the prepared loaf pan.
Smooth the top with a spatula.
Bake for 35–40 minutes or until a toothpick comes out clean.
Cool in the pan for 10 minutes.
Transfer to a wire rack and cool completely before slicing.
