Peel the ginger and grate it using a box grater with large holes. Blanch the tomatoes in boiling water for 10 seconds, cool under running water, peel, halve, seed, and chop the flesh. Peel and finely chop the onions.
Combine the onions, peanut oil, and 2 tablespoons water in a 24 cm non-stick pan. Cook over medium heat for 4-5 minutes until the liquid evaporates and onions turn golden. Stir in the ginger for 1 minute, then add the tomatoes. Season with salt and pepper. Boil vigorously for 2 minutes over high heat, add the prawns, and stir for 30 seconds to gently reheat without overcooking, which toughens them.
Transfer to a deep dish, sprinkle with Thai basil, and serve. Halve the Caribbean peppers and place alongside; let guests rub them on the shrimp for customizable heat—these potent peppers aren't for eating.
Pair with rice. Versatile with any prawns, from small to large, including crevettes, royals, or langoustines.
