Pat salmon fillets thoroughly dry with paper towels. Season both sides with 1/2 teaspoon kosher salt, black pepper, and Italian herb seasoning.
Heat olive oil and 1 tablespoon butter in a large skillet over medium-high heat. Add salmon fillets flesh-side down and sear undisturbed for 4-5 minutes until golden-brown crust develops. Flip and sear for 3 minutes. Transfer salmon to a plate.
Lower heat to medium. Add remaining 1 tablespoon butter to the skillet. Sauté minced garlic and diced shallot for 1 minute until fragrant. Add julienned sun-dried tomatoes and cook for 1 minute.
Pour in broth, scraping up any browned bits from the skillet bottom. Stir in heavy cream and bring to a gentle simmer for 3 minutes.
Stir in freshly grated parmesan cheese until melted and creamy. Add baby spinach and stir for 1-2 minutes until wilted.
Nestle seared salmon fillets back into the simmering sauce. Spoon sauce over the fillets and warm through for 2 minutes.
Finish with a squeeze of fresh lemon juice and fresh basil. Serve warm with pasta, mashed potatoes, or crusty bread!