Start by patting the salmon fillets dry with paper towels. Season both sides of each fillet with 2 teaspoons of Cajun seasoning and 1/2 teaspoon of smoked paprika.
In a large skillet, heat 1 tablespoon of olive oil over medium-high heat. Once the oil is shimmering, carefully place the salmon fillets in the skillet, skin-side down if applicable. Cook for about 4-5 minutes on each side, or until the salmon is cooked through and flakes easily with a fork. Remove the salmon from the skillet and set it aside on a plate.
In the same skillet, melt 1 tablespoon of butter. Add the diced onion and red bell pepper, sautéing for about 3-4 minutes until they’re softened. Stir in the minced garlic and cook for an additional minute until fragrant.
Pour in the chicken broth and let it simmer for about 2 minutes. Then, reduce the heat to medium-low and stir in the heavy cream, crushed red pepper flakes, black pepper, and 1/4 teaspoon of Cajun seasoning. If you prefer a thicker sauce, mix 1 to 2 teaspoons of cornstarch with a little water and add it to the sauce, whisking until it thickens.
Add the lemon juice and stir in the grated Parmesan cheese until it melts and the sauce becomes creamy. Taste and adjust seasoning if necessary.
Return the salmon to the skillet, spooning the creamy sauce over the fillets. Allow them to warm through for a minute. Serve the salmon garnished with sliced green onions and chopped fresh parsley for a burst of color and flavor.
