In a bowl, whisk together egg, egg whites, and tofu; season with salt and pepper.
In a small nonstick skillet, heat oil over medium-high; add bell pepper and scallion whites. Cook until scallion has browned, 3 to 5 minutes; transfer to a plate. Add egg mixture to skillet; cook, stirring occasionally with a rubber spatula, just until set, 2 to 3 minutes. Top with bell-pepper mixture and scallion greens.