In a large pot, bring salted water to a boil. Add the fettuccine and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain and set aside.
Season the salmon fillets with salt and pepper. In a large skillet, heat the olive oil over medium heat. Once hot, place the salmon skin-side down in the skillet. Sear for about 4-5 minutes until the skin is crispy, then carefully flip and cook for another 4-5 minutes until the salmon is cooked through. Remove from the skillet and flake into large pieces once cool enough to handle.
In the same skillet, add the minced garlic and sauté for about 30 seconds until fragrant. Then add the cherry tomatoes and cook for about 2-3 minutes until they start to soften.
Reduce the heat to low and add the heavy cream to the skillet, stirring to combine. Cook for about 2 minutes, then stir in the grated Parmesan cheese and lemon juice. Allow the sauce to thicken slightly, which should take another 2-3 minutes.
Add the cooked pasta and fresh spinach to the skillet with the cream sauce, tossing gently to coat everything evenly. If the sauce is too thick, add a little reserved pasta water to achieve the desired consistency.
Gently fold the flaked salmon into the pasta mixture, being careful not to break it up too much. Season with additional salt and pepper to taste.
Divide the creamy Tuscan salmon pasta among plates. Garnish with fresh basil leaves before serving.
Notes
Reserve pasta water to adjust sauce consistency if needed.