Heat a wok over high heat. Add 2 Tbsp oil, onion, capsicum and broccolini and stir-fry for 2 minutes, till just atarting to soften. Remove vegetables and set aside. Add prawns to wok with remaining 1 Tablespoon oil, reserving marinade and stir-fry for about 1 minute, until they just start to colour. Return vegetables to wok, add reserved marinade, lemon and water and cook, stirring constantly, until sauce boils. Add 1/4 bunch chopped coriander