In a small saucepan, bring the bulgur and 6 cups of water to a boil. Cook, uncovered, until tender, about 20 minutes. Transfer to a strainer and rinse under cold water. Shake to remove any excess water. Transfer to a large bowl and add the parsley, scallions, tomatoes, and cucumber.In a small bowl, whisk together the lemon juice, oil, salt, and pepper. Drizzle the vinaigrette over the bulgur and toss. Serve cold or at room temperature.