In mixing bowl or food processor, combine psyllium and boil water to form a gel. (If you don't have a high powered mixer or food processor, it's better to mix the psyllium with the other dry ingredients and then blend in the boiling water.)
Blend in almond flour, coconut flour, cream of tartar, baking soda, and salt.
Stream in melted butter (or ghee) and coconut oil until dough is formed.
Spread dough into a greased or parchment lined 8x4-inch loaf pan and smooth top.
Bake at 350°F for about 40-50 minutes or until top is brown and center is set.
Cool on rack 15 minutes then remove bread to cool completely on rack. Store in refrigerator or freezer unless consuming within a couple days.
The amount of butter could probably be reduced but has not been tested.2g net carbs per slice