In a small bowl, mix the lukewarm water, yeast, and sugar substitute. Allow it to sit for about 5-10 minutes until it becomes frothy.

Stir in the almond flour to form a thick paste. Cover the bowl loosely with a cloth or plastic wrap.

Let this mixture sit at room temperature for at least 12 hours or overnight. It should become bubbly and develop a slightly sour aroma.

Preheat your oven to 350°F (175°C).

In a large mixing bowl, combine almond flour, coconut flour, psyllium husk powder, baking powder, and salt.

In another bowl, whisk the eggs, apple cider vinegar, melted coconut oil, and 1/4 cup lukewarm water.

Add the egg mixture to the dry ingredients and stir until a dough forms.

Gradually add lukewarm water, one tablespoon at a time, until you achieve a smooth and pliable dough. The amount of water needed may vary, so be cautious not to add too much.

Add the sourdough starter to the dough mixture and combine thoroughly.

If the dough is too dry or stiff, you can add a little more lukewarm water to reach the desired consistency.

Shape the dough into a loaf and place it in a greased or parchment paper-lined bread pan.

Optionally, you can sprinkle some sesame seeds or other keto-friendly toppings on top of the loaf.

Bake in the preheated oven for about 50-60 minutes, or until the bread is firm, golden brown, and sounds hollow when tapped on the bottom.

Let the bread cool in the pan for a few minutes, then transfer it to a wire rack to cool completely.

Enjoy your keto-friendly sourdough bread! Keep in mind that this bread will have a different texture and flavor compared to traditional sourdough due to the absence of wheat flour, but it’s a great low-carb alternative.