Begin by cutting the yelloweye into equal fillets. Combine all the remaining ingredients reserving 1/2 tbsp of the cumin, coriander, garam masala and 1/2 of the lemon. Add the fish and coat on both sides. Put in fridge for 60 - 120 minutes.
Meanwhile, create the cucumber ribbons using a cheese peeler. Combine the other ingredients in a bowl and drop in the cucumber ribbons. This can be done 30 minutes before serving.
30 - 45 minutes before serving, make the pickled red onions by putting all the ingredients into a low bowl. Mix well and mix during the pickling process as well.
In a cast iron skillet, add the remaining oil and reserved spices. Cook for 1 minute to let the spice flavors release. Add the yelloweye and cook for 3 - 4 minutes per side.
To serve, place a few of the ribbons on a plate. Top with the tandoori curry seafood, and then, the red onions.