Place bulgur in a large bowl and add 1 1/2 cups boiling water. Let soak until softened and water is absorbed, 40-45 minutes.
Toss bulgur, cabbage, onion, tomatoes, mint, oil, lemon juice, and Aleppo pepper in a large bowl to combine; season with salt.
Do Ahead: Tabbouleh (without oil and lemon juice) can be made 4 hours ahead. Toss with oil and lemon juice just before serving.