Prepare the Salmon: Pat dry the salmon fillets and season with salt and black pepper.
Sear the Salmon: In a large skillet, heat olive oil over medium-high heat. Sear the salmon for 3-4 minutes per side until golden brown. Remove and set aside.
Make the Sauce: In the same pan, melt butter and sauté onion until translucent. Add minced garlic and cook for 30 seconds.
Add Creamy Elements: Pour in the heavy cream, chicken broth, Parmesan cheese, Dijon mustard, lemon juice, Italian seasoning, and red pepper flakes. Stir well and let it simmer for 3-4 minutes until slightly thickened.
Add Spinach: Stir in fresh spinach and cook until wilted.
Return Salmon: Place the salmon back into the skillet, spooning the sauce over the fillets. Simmer for another 2-3 minutes.
Serve: Let the salmon rest for 5 minutes before serving. Enjoy with pasta, rice, or mashed potatoes.