Prepare the rice according to package directions without the package of seasoning. Set aside to cool to room temperature.
In a large bowl combine the onions and tomatoes. Whisk together the oil, orange zest and juice and salt and pepper, to taste, in a small bowl. Pour the oil mixture over onions and tomatoes and add the cooled rice. Toss to combine, then cover the bowl and refrigerate until ready to serve. Can be served cold or at room temperature.