Line a large plate with several layers of paper towels. Arrange the tofu slices on top in a single layer, then cover with more paper towels and set another plate on top; let drain 5 minutes. Season the tofu with salt and pepper; rub with 1 1/2 tablespoons cornstarch. Whisk the lemon zest, 1/2 cup water, 1/2 teaspoon salt and the remaining 1/2 tablespoon cornstarch in a bowl; set aside. Heat 1 tablespoon vegetable oil in a large nonstick skillet over medium-high heat until very hot. Add the tofu and cook until golden brown, 3 to 4 minutes per side. Transfer to a plate. Add the remaining 1 tablespoon oil to the pan. Add the scallion whites and ginger and cook 30 seconds. Add the mushrooms and carrots and cook until just tender, about 3 minutes. Add the snap peas and 1/4 teaspoon salt; cook, stirring, 4 more minutes. Whisk the lemon zest mixture, add it to the pan and simmer 2 minutes. Stir in the scallion greens. Meanwhile, prepare the rice as the label directs. Serve with the tofu and vegetables.