Crispy Orange Cauliflower

Name: Crispy Orange Cauliflower
Ingredients: 1 teaspoon grated orange zest; 1 cup orange juice (from 3 oranges); 2 tablespoons light brown sugar; 2 tablespoons reduced-sodium soy sauce; 1 tablespoon cornstarch plus ¾ cup, divided; 1 tablespoon rice vinegar; 1 tablespoon toasted sesame oil; 1 teaspoon grated fresh ginger; 2 cloves garlic , grated; ⅛ teaspoon salt plus ¼ teaspoon, divided; 1 cup cold water , plus more as needed; ¾ cup all-purpose flour; ½ teaspoon baking powder; 3 cups neutral oil, such as canola or avocado; 1 medium head cauliflower , cut into 1½-inch florets (about 8 cups); Thinly sliced scallions and sesame seeds for garnish (optional)