Prep the ingredients by finely chopping the yellow onion and mincing the garlic cloves. Pat the salmon dry and season with salt and black pepper.

In a large nonstick skillet, heat the olive oil and butter over medium heat. Sear the salmon for 3-4 minutes on each side until golden brown.

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

Stir in the anchovy (if using), red chili flakes, salt, black pepper, dried oregano, dried sage, and sweet paprika. Cook for 1 minute.

Add the chicken broth into the skillet and let it simmer for about 2 minutes.

Mix in the crushed tomatoes and let the sauce simmer for about 5 minutes until it thickens.

Add the spinach to the skillet, stirring until just wilted, about 2-3 minutes.

Nestle the seared salmon back into the skillet, spooning some sauce over the top. Cook for an additional 3 minutes until cooked through.

Serve warm garnished with chopped parsley, red pepper flakes, and black pepper.