Bring the salmon to room temperature 10 minutes before cooking. Bring a large pot of salted water to a boil. Cook the spaghetti according to the package directions. Drain and toss with 1 teaspoon sesame oil and set aside.
Meanwhile, whisk together the miso, lime juice, 3 tablespoons of the vegetable oil, honey, garlic and remaining 1 teaspoon sesame oil in a large bowl.
Heat the remaining 3 tablespoons vegetable oil in a large skillet. Pat dry the salmon, then sprinkle with 1 teaspoon salt and 1/2 teaspoon pepper. Place in the skillet skin-side up; cook until the bottom is golden and crispy, 2 to 3 minutes. Flip the salmon and cook on all sides until opaque throughout, about 2 minutes per side.
When ready to serve, toss the spaghetti with the miso dressing, scallions, cucumber, chile and cilantro. Divide between plates and top with the crispy salmon.