Begin by filling a stock pot with water, almost to the top. Season the water with about a teaspoon of salt (optional), and bring it to a boil. Once the water is boiling, gently add the linguine noodles directly into the pot.
Boil the noodles until they are al dente, about 10-15 minutes. Be sure to stir them occasionally so that they do not stick together.
While the pasta is cooking, start with the salmon. Sprinkle the seasoned salt, paprika, garlic powder, black pepper, and onion powder evenly over the salmon filets.
Add the olive oil into a cast iron skillet and heat up over medium high. Place the salmon in one single layer, directly into the preheated oil.
Sear for 4 minutes and then flip to the other side and sear another 4 minutes. Remove the salmon from the skillet and set it aside.
Turn the heat down to medium. Add the unsalted butter into the skillet, and then add the garlic. Sauté the garlic for about one minute, stirring continually so that it does not burn.
Add in the tomato paste and stir around for about a minute. Next pour in the heavy cream, and stir until everything is fully combined and smooth.
If the sauce starts to get too thick, add in some of the water that the pasta is cooking in, add about one tablespoon at a time.
Next sprinkle in the parmesan cheese, and stir it up until it is melted and smooth.
Season the sauce with the Italian seasoning, black pepper, garlic powder, and salt.
Add in the spinach and stir it around until the spinach is wilted, about one minute or so.
Nestle the salmon back into the sauce. Turn the heat to low and let it simmer for about 5 minutes.
Serve over the pasta, and enjoy!