Cook pasta according to package instructions until al dente. Before draining, reserve ¼ cup of pasta water.
Pat the salmon fillets dry with a paper towel. Season both sides with paprika, garlic powder, lemon pepper, onion butter seasoning, and salt.
Heat a drizzle of olive oil in a large pan over medium heat. Add the salmon fillets and cook for about 3–4 minutes per side, or until the salmon reaches an internal temperature of 145°F. Remove the salmon from the pan and set aside.
Using the same pan, add butter and scrape up the flavorful browned bits from the bottom.
Add minced garlic and cook until fragrant or about 30 seconds.
Lower the heat and add milk (or cream) and reserved pasta water. Stir to combine.
Add freshly grated Parmesan cheese and stir until the sauce becomes smooth and creamy.
Season the sauce with garlic powder and lemon pepper to taste. Add fresh lemon juice and mix well.
Add the cooked pasta into the sauce and toss until evenly coated. Cook for an additional 1–2 minutes to allow the flavors to combine.
Plate the creamy pasta and top with the salmon fillets. Garnish with chopped parsley, chili flakes, extra Parmesan cheese, and a squeeze of fresh lemon juice if desired.