Clean the purchased prawns, cut off the whiskers, open the back and pick out the shrimp lines; prepare green onions and ginger, cut them into slices and minced ginger. Heat oil in a pan. When the oil is hot, add the prawns and stir-fry. At the same time, add the green onions and minced ginger. Stir-fry until the prawns change color, add two tablespoons of tomato sauce, continue to stir-fry for a while, add a little water, add a little salt, then cover the pot and simmer. After about three minutes, the soup in the pot is basically dry, you can turn off the heat, and the delicious tomato sauce braised prawns are ready.