Combine the quinoa and water in a small saucepan and bring to a boil over high heat. Cover, reduce the heat to low and simmer until the quinoa is tender and the water is completely absorbed, for about 10-15 minutes. Let cool.

Heat 2 tablespoons of the oil in a medium cast-iron skillet over medium-high heat until very hot. Add the corn kernels and cook, stirring constantly, until slightly blackened on the outside and barely cooked on the inside, about 30 seconds. Spread the corn on a plate in a single layer to cool.

Transfer the corn to a large bowl and add the quinoa, tomatoes, scallions, and parsley. Stir in the vinegar and remaining tablespoon olive oil and season with salt and pepper to taste. Set aside to marinate at least 30 minutes or up to 3 hours. Serve and enjoy!