1/2 small red or green chile, finely chopped
2 tablespoons fish sauce
2 tablespoons fresh lime juice
1 tablespoon sugar
2 garlic cloves, finely grated, divided
6 ounces thin vermicelli noodles
1 1/2-inch piece ginger, peeled, finely grated
1/2 teaspoon ground turmeric
3 tablespoons neutral oil, divided
3/4 pound boneless, skinless cod, cut into 2-inch pieces
Kosher salt, freshly ground pepper
1 bunch of dill, very coarsely chopped (about 2 cups)
4 scallions, white parts very thinly sliced lengthwise, green parts cut into 2-inch pieces
1/4 cup roasted, skin-on peanuts, coarsely crushed
Mix chile, fish sauce, lime juice, sugar, half of garlic, and 1/4 cup cold water in a small bowl until sugar dissolves; set nuoc cham aside.
Cook noodles according to package directions. Drain and rinse with cold water.
Mix ginger, turmeric, 2 Tbsp. oil, and remaining garlic in a medium bowl. Add fish and toss to coat; season with salt and pepper.
Heat remaining 1 Tbsp. oil in a medium nonstick skillet over medium-high until shimmering. Add fish mixture and cook, turning occasionally, until golden brown and just cooked through, 4–5 minutes. Add dill and scallion greens, toss a few times, then continue to cook until greens are barely wilted, about 30 seconds.
Divide noodles, fish mixture, and peanuts among bowls. Top with scallion whites. Serve with nuoc cham alongside.