Working with 1 beet at a time, cut off the ends and stand the beet upright on a cutting board. Peel the beets in strips, cutting from top to bottom and turning the beet as you trim. Slice the beets into 1/2-inch-thick slices and place in a large saucepan. Cover with water and bring the water to a boil. Add salt and cook the beets for 5 minutes. Drain the beets, run cold water over them, drain again and pat dry. Cut the beets into thick sticks.
While the beets cook, score the skin of the fish fillets by making a few shallow cuts in it. (The skin gets crispy and delicious.) Season the snapper by sprinkling the coriander and some salt and pepper evenly over the flesh side of the fillets. Dust the fish on both sides with some cornstarch. Get a platter and some foil ready-you will cook the fish in 2 batches.
Heat 2 large nonstick skillets over high heat, 1 for the fish and 1 for the beets and zucchini. Cover the bottom of 1 skillet with a thin layer of oil (1/8 inch deep). Add 3 fish fillets, skin side down, and cook for 3 to 4 minutes on each side, until crisp and firm. Transfer the cooked fish to a platter; cover loosely with a foil tent to keep warm. (Don'tcover the fish too tightly or it will become mushy.) Add more oil to the pan and cook the remaining 3 fillets.
While the second batch of snapper cooks, add 2 tablespoons of oil (2 turns of the pan) to the other hot skillet and stir-fry the beets and zucchini for 3 to 4 minutes, then add the scallions, ginger, garlic and crushed red pepper and cook a minute more. Add the plum sauce to the pan and heat through, glazing the veggies. Add the lime juice and remove from the heat. Serve the fish over the veggies and pass the lime wedges at the table.
Why You Should Score Your Meat, Fish and Veggies