Place the chicken between 2 sheets of plastic wrap. Pound with a mallet to ½-inch thickness. Combine the cumin with the cayenne and rub over the chicken.
Heat the oil in a large skillet over medium heat. Sauté the chicken for 4 minutes per side. Transfer to a cutting board.
Return the skillet with the pan drippings to medium heat. Add the onion and jalapeño. Cook, stirring, for 1 minute.
Add the beans, corn, tomatoes, and 3 tablespoons water and cook, stirring, 1 or 2 minutes, until just heated through. Remove from heat.
Toss with the scallions, cilantro, and vinegar. Season to taste with salt and black pepper. Slice the chicken and arrange on top of the beans.