For the salad:
1 tablespoon fish sauce
1 tablespoon grated, peeled fresh ginger (from about a 2- to 3-inch piece)
1 tablespoon freshly squeezed lime juice
1 tablespoon granulated sugar
1 medium garlic clove, minced
1 Thai bird chile, stemmed and minced
1 tablespoon vegetable oil
1 medium carrot, peeled and grated (about 1 cup)
1/2 English cucumber (about 8 ounces), sliced into 1/8-inch-thick rounds

For the tuna:
4 (1-inch-thick) sushi-grade tuna steaks (about 1 1/2 pounds)
Vegetable oil, for oiling the tuna and the grill
Kosher salt
Freshly ground black pepper

To serve:
2 tablespoons coarsely chopped fresh cilantro
2 tablespoons coarsely chopped roasted, salted peanuts