Preheat and prep. Heat your oven to 400°F (205°C). Line a sheet pan with parchment or lightly grease it with olive oil or butter. Pat the salmon dry with paper towels and set it skin-side down if using skin-on fillets.

Make the horseradish topping. In a bowl, mix prepared horseradish, mayonnaise, sour cream, Dijon, lemon juice and zest, garlic, and chopped herbs. Stir in Parmesan if using. Taste and season with salt and pepper. It should be zippy, creamy, and well seasoned.

Season the salmon. Brush the tops lightly with olive oil or melted butter. Sprinkle with salt and pepper. This helps the topping adhere and seasons the fish itself.

Spread the topping. Spoon the horseradish mixture over each fillet, spreading it to the edges in an even layer about 1/8–1/4 inch thick. Don’t skimp—this keeps the salmon moist.

Bake to tender and flaky. Place the pan on the middle rack and bake 12–15 minutes, depending on thickness. Aim for an internal temperature of 125–130°F (52–54°C) for medium and super-juicy results. The topping should be set and lightly golden.

Optional broil. For extra color, broil for 1–2 minutes at the end. Watch closely so it doesn’t burn.

Rest and serve. Let the salmon rest 3 minutes. Finish with a squeeze of lemon and extra herbs. Serve with simple sides like roasted asparagus, sautéed spinach, or a crisp cucumber salad.