1. Adjust oven rack so that it sits about 4 inches from heating element. Preheat broiler. Combine the ginger, 2 cloves of garlic, coriander, lemon zest, and olive oil in a small bowl. Arrange salmon fillets on baking sheet. Season with salt and pepper and spread mixture onto the top of salmon fillets. Set aside while preparing the salad.
2. In a medium bowl, combine the cucumber, radishes, yogurt, cilantro, 1 clove of garlic, 1 tablespoon lemon juice, and season to taste with salt and pepper.
3. Broil salmon until ginger crust turns golden and slightly crispy and a peek at inside of fish with paring knife shows that they are just cooked through, 6 to 8 minutes. Transfer salmon to serving platter or individual plates and serve with cucumber salad.