Place a cast iron pan over medium-high heat. Add olive oil.
Cut salmon into 2 or 3 pieces and season with salt and pepper.
Once the oil is hot, add salmon to the pan and cook on both sides for about 2-3 minutes. The salmon should still be slightly pink in the center.
Remove salmon from pan and transfer to a plate, cover with foil. Set aside.
Add diced onion to the same pan and cook for 1 minute stirring from time to time. Add minced garlic and chopped sun dried tomatoes. Stir and cook for another minute.
Add fresh spinach, stir and cook for 1 minute and add salt, pepper, dried basil and Italian seasoning herbs. Stir and toss until the spinach is wilted.
Add heavy cream, stir to combine and cook for a few minutes, until the cream just slightly starts to simmer.
Reduce heat to low-medium.
Add grated parmesan cheese and stir until the cheese is fully melted. Taste and adjust the sauce for salt and pepper.
Add the salmon back to the pan, skin side down, scoop and pour some of the sauce on top of the salmon and cook it in the sauce for about 3-5 minutes, or until heated through. Baste the salmon from time to time.