Preheat your oven to 425° F and add 8 paper or foil muffin liners to a muffin tin.
In a large-mixing bowl, whisk together the lemon juice, lemon zest, vanilla, agave, sugar, and ground chia. Set bowl aside.
In a medium-sized mixing bowl, stir together the oat flour, protein powder, salt, baking powder, baking soda, and xanthan gum.
Pour the kombucha into the first bowl with the wet ingredients, quickly add in the dry ingredients, as well as, the blueberries, and using a silicon spatula, or wooden spoon, gently stir the ingredients just until fully incorporated, being careful not to over mix.
As soon as everything is combined, distribute batter into your lined muffin tin. Portion each muffin with about 1/4 cup of the batter (I use a 2 oz portion scoop).
Once the muffins are portioned, transfer immediately to the preheated oven. Bake for 5 minutes at 425° F, then without opening the oven, lower the oven temperature to 375°F and bake for an additional 15 minutes.