Prepare a loaf tin by greasing it with oil and dusting it with a little buckwheat flour.
Mix together the yeast, honey, and warm water in a bowl, then set aside for 15 minutes.
Add the psyllium husk powder, whisking it in well, then set the mixture aside for another 10 minutes, until the mixture is gelatinous.
In a bowl, whisk together the buckwheat flour, tapioca starch, xanthan gum, and sea salt.
In a stand mixer fitted with a dough hook attachment, combine the dry ingredients with the wet ingredients and the apple cider vinegar to form a wet dough.
Dust a clean surface with a little buckwheat flour, then turn out the dough onto the floured surface.
Shape the dough into a log and carefully transfer to the prepared loaf tin.
Cover with a towel and set the dough aside somewhere warm to rise for 1 hour.
While the dough rises, preheat the oven to 425 F.
After rising, remove the towel and bake the bread for 1 hour 45 minutes.
Turn the baked bread out and let it cool completely before cutting and serving.