Preheat the oven to 425°F and prepare a baking sheet with parchment paper. Pull any pin bones out of the salmon with fish bone tweezers. Pat the salmon dry with paper towel.
Bring a large pot of water to a rolling boil, add 2-3 tablespoons of kosher salt per pound of pasta, and cook the pasta according to package instructions until al dente. For best results, we recommend cooking the pasta for the lowest amount of time suggested, as it will finish cooking into the sauce. Make sure to reserve 2 cups of pasta water. Drain pasta and don't rinse! You can toss the cooked pasta with a drizzle of olive oil to prevent the noodles from sticking together.
Mix the seasoning blend together in a small bowl and set aside.
Place the salmon skin side down on a prepared baking sheet. Drizzle the salmon with olive oil and lemon juice. Season salmon with salt, about half of the seasoning blend, and the lemon zest. Coat the salmon well on all sides. Bake the salmon for 12-15 minutes, or until salmon reaches an internal temperature of 145°F, and set aside.
Meanwhile, make the cream sauce. Add olive oil and butter to melt. Then, add the onion and a good pinch of salt. Cook until onion is softened and translucent, about 5-7 minutes.
Add in the remaining butter, along with the garlic, the remaining dried seasonings, and lemon zest. Cook for 1 minute until the garlic is fragrant, stirring often to ensure the garlic doesn't burn. As soon as the garlic is fragrant, immediately deglaze the pan with white wine. Bring mixture to a boil, then reduce to a simmer immediately. Cook for 3-5 minutes to cook off the alcohol.
Reduce to low heat, then pour in the cream. Add in freshly grated parmesan cheese in small handfuls, stirring to melt completely before adding more cheese until a sauce forms. This should take about 3-5 minutes.
Now, add in the spinach with a pinch of salt, and stir to wilt. Slowly drizzle in pasta water to help wilt the spinach and form the sauce.
Add the cooked pasta to the pan along with fresh lemon juice, and a little more pasta water. Toss until the sauce coats the noodles then remove from the heat.
Break the roasted salmon into large chunks using a fork, then place it on top of the pasta. Garnish with more parmesan cheese, fresh herbs, and lemon slices. Enjoy!
Store leftovers in an airtight container in the fridge for up to 3 days. Do not freeze.