Preheat oven to 350F; generously grease an 8½ by 4½-inch loaf pan with ghee or coconut oil.
Whisk together the almond meal, arrowroot starch, flaxseed meal, tapioca starch, salt, and baking soda in a large bowl.
Whisk together the slightly cooled butter or coconut oil, eggs, almond “milk”, and vinegar in a medium bowl.
Add the wet ingredients to the dry all at once and stir until combined, being careful not to over-mix. The batter will be thick.
Immediately pour the batter into the prepared pan and bake until a toothpick inserted into the center comes out clean, about 40 to 45 minutes in a glass pan.
Cool on a wire rack before slicing and serving, and store any leftovers wrapped in the fridge for up to 5 days.
Net Carbs: 6g per serving (1 slice)Update January 20, 2016: I received a lot of emails with different questions about making this bread. I've done several additional rounds of testing and have made slight updates to the recipe, and here are my tips.Cooking Time: I use a glass loaf pan to make this bread. If you use a metal loaf pan, you may need to adjust the cooking time because although glass takes a bit longer than metal to heat up, once it's hot, it retains heat better.Troubleshooting Why Your Loaf Didn't Rise: Be sure to use the same size baking dish that the recipe specifies; make sure your oven is properly calibrated; preheat your oven before baking; use fresh baking soda; don't skip the vinegar. Also please note that by nature paleo bread doesn't rise as much as regular bread with gluten.Brands of Almond Flour I've Used: I've successfully made this recipe with Bob's Red Mill, Honeyville, and Anthony's almond flour. If you use almond meal instead of almond flour, your bread will be darker.Substitutions: I have tested the following substitutions with good results:
No Arrowroot Starch: Omit the arrowroot starch; add 1 large egg white and increase the tapioca starch to 4 tablespoons (30 g).
Golden Flaxseed Meal: Brown flaxseed meal will also work, but you'll have specks of brown in your loaf. You can make your own flaxseed meal by finely grinding flaxseeds, but do not use whole flaxseeds for this recipe.
Ghee or Coconut Oil: Unsalted butter (melted and cooled slightly) will also work.
Plain, Unsweetened Almond "Milk": Cow's milk will also work (I tested this recipe with both whole milk and 2% milk with good results). Other types of milk may also work, but I haven't tested them (if you make this with another type of milk, please let us know how it goes in the comments!).
Correction in Video: At 0:21, the video says "baking powder", but the correct ingredient is actually baking soda like the recipe says.