Preheat the oven to 425°F. Lightly spray a baking sheet with cooking spray.

Place the salmon on the prepared baking sheet and sprinkle with 1 teaspoon salt. Bake until just opaque in the center, 20 to 25 minutes.

While the salmon is baking, melt the butter in a medium sauté pan over medium heat. Add the flour and stir until it becomes a smooth paste. Add the milk, whisking constantly, and cook over medium heat until the sauce begin to boil and thicken. Simmer over low heat, whisking constantly, for 5 minutes. Stir in the heavy cream, lemon zest and juice, dill, and salt and pepper to taste. Remove from the heat.

Transfer the salmon to a serving platter and pour the sauce over it to serve.

Preheat the oven to 425°F. Lightly spray a baking sheet with cooking spray.

Place the salmon on the prepared baking sheet and sprinkle with 1 teaspoon salt. Bake until just opaque in the center, 20 to 25 minutes.

While the salmon is baking, melt the butter in a medium sauté pan over medium heat. Add the flour and stir until it becomes a smooth paste. Add the milk, whisking constantly, and cook over medium heat until the sauce begin to boil and thicken. Simmer over low heat, whisking constantly, for 5 minutes. Stir in the heavy cream, lemon zest and juice, dill, and salt and pepper to taste. Remove from the heat.

Transfer the salmon to a serving platter and pour the sauce over it to serve.