For the Salmon: Season the salmon fillets with salt and pepper on both sides. In a large skillet, heat the olive oil over medium-high heat. Add the salmon fillets, skin-side down, and cook for 4-5 minutes on each side, or until the salmon is cooked through and has a nice golden crust. Remove the salmon from the skillet and set aside.
For the Creamy Florentine Sauce: In the same skillet, melt the unsalted butter over medium heat. Add the minced garlic and finely chopped onion, and sauté for 2-3 minutes until the onion is softened and the garlic is fragrant. Pour in the heavy cream and chicken broth, stirring well to combine. Bring the mixture to a simmer. Stir in the grated Parmesan cheese until the sauce is smooth and thickened. Add the chopped spinach and sun-dried tomatoes, and cook for another 2-3 minutes until the spinach is wilted. Season the sauce with salt and pepper to taste.
To Serve: Place the pan-seared salmon fillets on plates and spoon the creamy Florentine sauce over the top. Garnish with freshly chopped parsley and a squeeze of fresh lemon juice if desired.
