Prepare the pickled cucumber salad by combing vinegar and sugar in a small saute pan and heating over low heat just until sugar dissolves. Add 2 tablespoons extra virgin olive oil and the cucumber; slightly warm the cucumber. Remove from the heat and lightly season with salt. Let the salad marinate for 30 minutes. Drain off any excess liquid and season the salad with salt and pepper as needed. Season the hamachi fillets with salt and pepper and dust each fillet on both sides with tandoori powder. Coat the fillets in the remaining extra virgin olive oil. Place a skillet over medium heat and gently sear the fillets, about 1 minute on each side. There should be a little color on each side and the fish should be rare in the middle but not cold. Warm the cranberry lemongrass sauce in a small saucepan. To serve, place the cucumber salad in a 1-inch ring mold on one side of each plate. Slice each hamachi fillet into 1/4-inch slices, about 6 slices per fillet. Shingle the slices down the other side of the plate. Squeeze fresh lemon juice over the hamachi and spoon 2 tablespoons of the Cranberry-Lemongrass Sauce around the fish.