01 - Pat the salmon fillets dry with paper towels. Season both sides generously with 1/2 teaspoon salt and 1/4 teaspoon black pepper, ensuring even coverage.
02 - Heat 2 tablespoons olive oil in a large skillet over medium-high heat until shimmering. Add salmon fillets skin-side down if using skin-on. Sear for 4 minutes until golden, then carefully flip and cook for 2-3 minutes until almost cooked through. Transfer to a plate and set aside.
03 - Reduce heat to medium. Add 2 tablespoons butter to the same skillet and let melt. Add minced garlic and diced onion, sautéing for 2-3 minutes until fragrant and translucent, being careful not to brown the garlic.
04 - Stir in the sliced sun-dried tomatoes and cook for 1 minute to release their flavors, allowing them to soften slightly in the butter mixture.
05 - Pour in the heavy cream and broth, using a wooden spoon to scrape up any browned bits from the bottom of the pan. Bring the mixture to a gentle simmer, stirring occasionally.
06 - Add Parmesan cheese and Italian seasoning to the simmering liquid. Stir continuously until the cheese completely melts and the sauce thickens slightly, about 2 minutes. The sauce should coat the back of a spoon.
07 - Add the baby spinach leaves to the sauce, tossing gently with tongs. Cook for just 1-2 minutes until spinach is wilted but still vibrant. Taste and adjust seasoning with additional salt and pepper as needed.
08 - Return the salmon fillets to the skillet, spooning the creamy sauce generously over each piece. Simmer gently for 2-3 minutes until salmon is cooked through and sauce is heated. Serve immediately, garnished with fresh basil leaves and lemon wedges if desired.