Preheat the oven to 350 °F.
In a large bowl, mix all the donair meat dry ingredients.
2 cups gluten flour, 2 ½ tablespoons nutritional yeast, 2 teaspoons onion powder, 2 teaspoons garlic powder, 1 ½ teaspoons dry oregano, 1 ½ teaspoons dry basil, 1 teaspoon celery seed, 1 teaspoon smoked paprika, 1 teaspoon ground turmeric, 1 teaspoon salt, black pepper
In a separate, medium-sized bowl, mix together all the donair meat wet ingredients.
½ cup onion, ¼ cup olive oil, 4 tablespoons ketchup, 3 tablespoons soy sauce, 1 ½ tablespoons apple cider vinegar, 1 tablespoon Dijon mustard, ¾ cup vegetable broth
Pour the wet ingredients into the dry ingredients and stir together. Once most of the liquid is absorbed, use your hand to knead the dough until everything is evenly mixed together.
Place two sheets of tin foil on the counter (shiny side up). The pieces should be about 1 ½ feet long.
Put the seitan dough onto one of the tin foil sheets and press into a rectangular shape, about 6 inches wide and 1 – 1 ½ inches thick.
Carefully wrap the seitan dough in the tin foil. It’s often best to fold up the bottom edge (away from you), then fold in both sides, then fold down the top. Place the rough edge of the tin foil-wrapped seitan down onto the second sheet of tin foil and repeat the folding.
Place the double-wrapped seitan onto a baking sheet and place into the oven. Cook for 30 minutes, flip the seitan over and cook for another 20 minutes.
Take the seitan out of the oven and let sit for 5 – 10 minutes before unwrapping the tin foil. Allow seitan to cool for as long as possible (as it cools it will set and become easier to cut).