In a medium nonstick skillet, heat 1 teaspoon oil over medium. Add bell pepper and cook until softened, 5 to 7 minutes. Add scallion, corn, and cumin and cook until scallion has wilted, 2 to 3 minutes; season with salt and pepper. Remove to a plate and cover with foil to keep warm. Wipe skillet with a paper towel; reserve skillet.
In a large bowl, whisk together eggs and whites, 1/2 teaspoon salt, 1/8 teaspoon pepper, and 2 teaspoons water until well combined. In reserved skillet, heat remaining teaspoon oil over medium. Add egg mixture and cook until bottom is set, 30 seconds. Gently stir with a spatula to bring cooked curds up from the bottom of the pan. Continue to cook, stirring occasionally, until cooked through, about 1 1/2 minutes. Stir in cheese and reserved vegetables. Serve with salsa, avocado, and tortillas.