Blend the chickpea flour, silken tofu, milk, cornstarch, baking powder, garlic powder, salt, black pepper, and turmeric until completely smooth. Let the batter stand for 5 minutes so the chickpea flour can hydrate.
Melt half of the butter in a 10-inch nonstick skillet over medium heat. Add the bell pepper and cook for 2 to 3 minutes until slightly softened, then transfer it to a plate.
Reduce the heat to medium-low and melt the remaining butter in the skillet. Pour in the omelet batter and immediately spread it into an even layer.
Cover the skillet and cook for 5 to 7 minutes, until the surface is mostly set and the underside is golden. The slower cooking time is important for removing the raw chickpea flour flavor while keeping the center tender.
Sprinkle the cheddar, cooked bell pepper, and green onions over one half of the omelet. Fold the other half over the filling and cover again.
Cook for another 2 minutes, until the cheese is melted and the center is fully set. Transfer to a plate and serve immediately.
