Preheat the broiler.
Place the peppers on a baking sheet and broil until the skin is blistered and charred, turning to cook on all sides, 1 to 2 minutes per side. Place the charred peppers in a bowl and cover with plastic wrap to cool for at least 10 minutes. Once cool, remove the skin easily with your hands.
Meanwhile, in a medium bowl, use a hand mixer to beat the egg whites to stiff peaks. In a small bowl, mix 2 egg yolks with 1 tablespoon flour and 1/2 teaspoon salt. (Reserve 2 remaining yolks for another use.). Place the remaining flour on a small plate. Mix one-third of the egg whites into the egg yolks, and then gently fold the egg yolk mixture into the remaining egg whites just until incorporated. In a third bowl, mix together the cheese and corn.
Remove the seeds from the peppers by slicing them open along one side. Slice about two-thirds the length of the pepper, just long enough to remove the seeds with a small spoon. Stuff the peppers with the cheese mixture, squeezing the cheese gently so that it stays together.
Heat 1 1/2 inches of oil in a large saucepan over medium-high heat. Gently roll the peppers in the flour. (If the cheese and peppers are too warm and are falling apart, place in the freezer for 10 minutes). Coat the peppers in the egg batter by dunking and spooning the batter all around. Lift the pepper, and gently spoon off any excess batter hanging from the bottom. Place in the hot oil and fry until golden, about 3 minutes per side. Place on paper towels to absorb the excess oil. Serve with Chile Relleno Tomato Sauce.
Add the olive oil to a medium saute pan over medium heat. Then add the onions and cook until softened, about 5 minutes. Add the cumin, cayenne and garlic, and cook until fragrant, 1 minute longer. Add the chicken stock and the tomatoes with their juice and bring to a boil for 1 to 2 minutes. Remove from the heat and cool a few minutes. Mix in the blender for 10 seconds (the sauce will not be smooth). Add the cilantro, vinegar, salt and pepper to taste and pulse just to blend.