In a medium bowl, whisk both flours with the onion powder, cayenne and a generous pinch of salt and black pepper. Whisk in the seltzer and scallions. The batter should be the consistency of pancake batter.
Heat 1/4 cup of the oil in each of two 10-inch skillets until shimmering. Divide the batter between the pans, gently shaking them and swirling to coat the bottom. Cook over high heat until the bottoms are golden and the pancakes are nearly set and golden on the bottom, about 3 minutes. Flip the pancakes and cook until golden and crisp, about 3 minutes longer. Drain on paper towels and sprinkle with salt. Cut each pancake into quarters and serve.