Bring a large pot of water to a boil and cook the whole wheat fettuccine according to the package instructions until al dente.
While the pasta cooks, season the salmon fillet with half of the sea salt and black pepper.
Heat the olive oil in a non-stick skillet over medium-high heat and sear the salmon for 4 to 5 minutes per side until golden and flaky.
Remove the salmon from the skillet, let it rest for 2 minutes, then flake it into large chunks using a fork.
In a small mixing bowl, whisk together the Greek yogurt, lemon juice, lemon zest, minced garlic, and chopped fresh dill to create the sauce.
Reserve 2 tablespoons of the pasta cooking water, then drain the noodles and return them to the warm pot.
Add the yogurt sauce, reserved pasta water, and fresh baby spinach to the pot, tossing gently until the spinach begins to wilt.
Fold in the flaked salmon and the remaining sea salt and black pepper, then serve immediately while warm.