In an airtight container, place the tofu, cabbage, bok choy, and radishes. In a separate container, mix the watermelon juice and tangy soy-vinegar sauce to make the ponzu sauce. Place the black and white sesame seeds and scallions in a separate container or small plastic bag and store everything in the fridge.
Place tofu and veggies in a serving dish and drizzle with watermelon ponzu sauce. Garnish with sesame seeds and scallions.