Season the salmon. Pat the fillets dry and sprinkle both sides with salt and pepper.
Sear the fish. Heat olive oil in a large skillet over medium-high.
Add salmon, skin-side down if using, and cook 3–4 minutes per side until golden and nearly cooked through. Transfer to a plate.
Start the sauce. Reduce heat to medium. Add butter to the same pan.
Stir in the garlic and sun-dried tomatoes, and cook for about 30 seconds until fragrant.
Build the cream base. Pour in chicken broth and scrape up any browned bits. Stir in heavy cream, Italian seasoning, and red pepper flakes. Simmer 2–3 minutes to slightly thicken.
Add greens and cheese. Stir in spinach and let it wilt.
Add Parmesan and simmer another minute until the sauce is creamy.
Finish with brightness. Stir in lemon juice. Taste and adjust salt and pepper.
Return the salmon. Nestle fillets into the sauce. Spoon sauce over the top and simmer 1–2 minutes until the salmon is just cooked through and flakes easily.
Serve. Garnish with fresh basil if you like.
Pair with cauliflower rice, zucchini noodles, or roasted asparagus.