Sweet-Sour Stir-Fry with Walnuts

For The Glaze:

• 1/2 cup orange juice (from 1 medium orange)
• 2 tablespoons cider vinegar
• 1 tablespoon soy sauce
• 1 tablespoon brown sugar or honey
• 1 tablespoon minced fresh ginger
• 2 teaspoons minced garlic (2 good-sized cloves)
• 1 teaspoon toasted sesame oil
• 1/2 teaspoon red pepper flakes
• 1 tablespoon cornstarch

For The Stir-Fry:

• 2 tablespoons canola oil
• 1 medium onion, cut into large (1 1/2-inch) squares
• 3/4 teaspoon salt
• 2 medium carrots, sliced on the diagonal (1/4-inch thick)
• 1/2 a medium head cauliflower, in 1-inch florets (about 3 cups)
• 1/2 a medium head broccoli, chopped (about 3 cups)
• About 15 mushrooms–stems trimmed, wiped clean, and quartered
• 1 pound very firm tofu, cut into 3/4 -inch cubes
• 2 small zucchini (one yellow, one green), chopped or diced
• 1 medium red bell pepper, cut into 1-inch squares
• 1 1/2 cups lightly toasted California walnut pieces
• Green onions, thinly sliced, for garnish
• Orange zest, for garnish