Finely chop one onion and mince three cloves of garlic. Pat the salmon fillets dry with a paper towel.

In a large skillet, heat two tablespoons of olive oil and one tablespoon of butter over medium-high heat. Sear salmon for 3-4 minutes skin-side down, flip and cook for another 3-4 minutes.

Lower the heat and sauté the chopped onion and minced garlic for about 2 minutes until translucent and fragrant.

Add one anchovy fillet and a teaspoon of chili to the skillet. Stir in one tablespoon of tomato paste and cook for one minute.

Deglaze with one cup of chicken broth and stir in the crushed tomatoes. Simmer for about 5 minutes until the sauce thickens.

Add the spinach, stirring until wilted. Nestle the salmon fillets back into the sauce and sprinkle with Parmesan cheese before serving.