Make the ponzu sauce: In a mixing bowl whisk together 1/2 cup low-sodium soy sauce, 1/2 cup citrus juice (lemon and/or orange), 2 tablespoons water, 1 teaspoon lemon zest, and 2 tablespoons mirin until combined; taste and adjust sweetness or salt as desired.
Press the tofu: Place the tofu block on a plate lined with paper towels, top with another plate and place a weight (such as cans) on top. Let sit 15 minutes to press out excess liquid, then discard accumulated water.
Slice and season the tofu: Slice the pressed tofu into 1/2" thick slices and pat both sides very dry. Brush each side with 3 tablespoons low-sodium soy sauce.
Pan-fry the tofu: Heat 1 tablespoon cooking oil in a frying pan over medium-high heat until shimmering. Add tofu slices and fry 2 minutes until golden, brush with more soy sauce, flip and fry 1 minute more, brushing again with soy sauce as desired.
Toast sesame seeds: In a dry small pan over medium heat, toast 4 teaspoons sesame seeds until fragrant, about 1–2 minutes, stirring constantly to prevent burning.
Assemble bowls: Divide 2–3 cups cooked quinoa or chosen grain (or greens for low carb) among four large bowls. Add 4–6 cups mixed vegetables of choice and top with the crispy tofu slices.
Finish and serve: Drizzle the ponzu sauce over each bowl and sprinkle with toasted sesame seeds before serving.