Preheat your oven to 375°F (190°C) to ensure even baking.
Pat the salmon fillets dry with paper towels and season both sides generously with salt and black pepper.
In a skillet over medium heat, melt the salted butter. Add the thinly sliced shallots and lightly smashed garlic cloves, sautéing for 2-3 minutes until translucent and fragrant.
Stir in fresh thyme leaves and a pinch of chili flakes. Pour in heavy cream and salsa verde, mixing well. Let the sauce simmer gently for about 5 minutes to thicken slightly.
Gradually add grated parmesan cheese and chopped sun-dried tomatoes. Cook for another 2-3 minutes until the cheese melts and sauce is creamy and smooth.
Add fresh baby spinach to the sauce and stir until wilted, about 1 minute. Remove skillet from heat and mix in lemon juice and zest.
Place the seasoned salmon fillets skin-side down in a prepared baking dish. Pour the creamy garlic butter sauce evenly over the salmon.
Bake in the preheated oven for 15-20 minutes, until salmon is cooked through and flakes easily with a fork (internal temperature 145°F / 63°C).
Remove from oven and sprinkle fresh chopped dill and green onions on top. Serve immediately, optionally garnished with extra lemon wedges.