01 - Pat the salmon fillets dry with paper towels and season both sides generously with salt and black pepper.
02 - Heat olive oil in a large skillet over medium-high heat. Add salmon fillets, skin-side down if using skin-on, and sear for 4 minutes. Flip and cook for 2-3 minutes until golden and nearly cooked through. Remove salmon from skillet and set aside.
03 - Reduce heat to medium. Add butter to the skillet and let melt. Add garlic and onion, sautéing for 2-3 minutes until fragrant and translucent.
04 - Stir in sun-dried tomatoes and cook for 1 minute to release their flavors.
05 - Pour in heavy cream and broth, scraping up any browned bits from the bottom of the pan. Bring to a gentle simmer.
06 - Add Parmesan cheese and Italian seasoning. Stir continuously until cheese melts completely and sauce thickens slightly, about 2 minutes.
07 - Add baby spinach and cook for 1-2 minutes until just wilted. Adjust seasoning with additional salt and pepper as needed.
08 - Return salmon fillets to the skillet, spooning sauce generously over each piece. Simmer gently for 2-3 minutes until salmon is cooked through and sauce reaches desired consistency.
09 - Serve hot, garnished with fresh basil leaves and lemon wedges if desired.