Add vital wheat gluten, nutritional yeast, garlic powder, onion powder, salt, and pepper to large bowl. Mix well to thoroughly distribute ingredients.
Slowly add 2 cups vegetable broth and 2 tablespoons olive oil to bowl, stirring constantly until all ingredients are fully combined to create dough.
Transfer dough from bowl to flat surface covered in plastic wrap. Knead dough to form ball, then divide ball of dough into two equal pieces.
Add 5 cups vegetable broth to large pot over medium-high heat. Bring broth to boil, then reduce heat to low and let broth simmer. Once broth is no longer boiling, add seitan to pot and cover with lid. Simmer covered 25 minutes, then transfer cooked seitan to large bowl or plate to cool.
In one shallow bowl, whisk together all vegan buttermilk ingredients until mixture is fully incorporated. Set aside.
In other shallow bowl, whisk together all ingredients for breading until ingredients are fully incorporated. Set aside.
Add enough oil to submerge seitan tenders in medium pot. Heat uncovered over medium-high heat until oil temperature reads 350° Fahrenheit.
Once seitan is completely cooled, break seitan into pieces resembling chicken tenders. Dip seitan tenders first in vegan buttermilk, coating both sides well. Let excess buttermilk drip back into bowl, then dredge seitan through flour mixture. Shake excess flour mixture back into bowl.
Drop breaded seitan tenders in hot oil. Fry seitan until golden brown, then transfer to plate lined with paper towels or wire cooling rack. Repeat process until all seitan tenders have been breaded and fried. Serve fried tenders warm with desired dipping sauces and sides.