For the Pickled Red Cabbage – Bring the vinegar, water, sugar, salt, and spices to a boil in a small pan. Place the red cabbage in a heatproof bowl, and pour the boiling liquid over the top. Cover and leave to cool, then refrigerate overnight, preferably.
For the Lime Sour Cream – Combine the Sour cream with the lime juice and zest in a small bowl. Season to taste and set aside.
For the Pico de Galo – In another small bowl, combine the freshly chopped vegetables and season with the lime juice and some salt to taste.
For the Blackened Prawns – In a small bowl, mix the prawns with the Cajun seasoning and season with salt to taste. Heat a medium-sized frying pan over a medium heat, and gently melt the butter. When the butter begins to bubble, add the prawns. Cook for 2-3 minutes until the prawns start to brown, then turn them over. Cook for 2 minutes, spooning the butter over the prawns and basting the prawns with the blackened mix. Drain the prawns off and assemble the tacos.
To Assemble the Tacos – Gently warm the tortilla in the same pan. Spoon in a tablespoon of drained red cabbage, followed by prawns, Pico de Galo, avocado, and lime sour cream. Finish with coriander.