Preheat your oven to 300°F (150°C). Prepare a 4x4 inch square pan by lining it with parchment paper or greasing it.

In a mixing bowl, whisk together the eggs and avocado oil until frothy, about 2–3 minutes. If using, add erythritol here and mix until dissolved.

Add the Greek yogurt to the egg and oil mixture and stir gently until smooth.

In a separate bowl, whisk together the almond flour, protein powder, baking powder, xanthan gum, and salt.

Slowly fold the dry ingredients into the wet mixture until just combined, being careful not to overmix.

Pour the batter into the prepared pan and smooth the top. Bake for 50–55 minutes until golden brown and a toothpick inserted comes out clean.

Allow the bread to cool in the pan for about 15 minutes before transferring to a wire rack to cool completely.