Season the salmon fillets with salt and pepper on both sides.
Heat olive oil in a large skillet over medium heat.
Place salmon in the skillet, skin-side down, and cook for 4–5 minutes per side until golden and cooked through. Remove and set aside.
In the same skillet, add butter and minced garlic. Sauté for about 1 minute until fragrant.
Add cherry tomatoes and cook until they begin to soften, about 2 minutes.
Add spinach and stir until wilted.
Pour in the heavy cream and Parmesan cheese. Stir and cook until the sauce thickens, 2–3 minutes.
Season with red pepper flakes if using.
Return the salmon to the skillet and spoon the sauce over it.
Serve warm with your choice of side.