01 - Pat the salmon fillets completely dry with paper towels. Season both sides generously with 1/2 teaspoon salt and 1/4 teaspoon black pepper, pressing the seasoning gently into the flesh.
02 - Heat olive oil in a large skillet over medium-high heat until shimmering. Place salmon fillets in the pan, skin-side down if using skin-on. Sear for 4 minutes until golden. Carefully flip and cook for 2-3 minutes longer until almost cooked through. Transfer salmon to a plate and set aside.
03 - Reduce heat to medium. Add 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 oils and intensify flavor.
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.
06 - Add the grated Parmesan cheese and Italian seasoning. Stir continuously until the cheese completely melts and the sauce thickens slightly, about 2 minutes.
07 - Add the baby spinach leaves to the simmering sauce. Cook for 1-2 minutes, stirring gently, until just wilted. 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 the salmon is cooked through and the sauce is velvety. Serve immediately, garnished with fresh basil leaves and lemon wedges on the side.