1 pound salmon, skin-on
2 and 1/2 tablespoons olive oil, divided
1 teaspoon lemon zest
1 tablespoon fresh lemon juice
4 cloves garlic, minced, divided
1 teaspoon dijon mustard
3/4 teaspoon onion powder
1/2 teaspoon salt
1/2 teaspoon black pepper
1/2 lemon, thinly sliced
1 pound asparagus, tough ends trimmed
1/2 cup finely shredded parmesan
Preheat oven to 400 degrees. Line a rimmed baking sheet with parchment paper. Place salmon in center of pan. In a small mixing bowl, whisk to combine 1 and 1/2 tablespoons olive oil, lemon zest, lemon juice, 2 cloves minced garlic, dijon, and onion powder. Brush evenly over salmon, then sprinkle with 1/2 teaspoon salt and 1/2 teaspoon pepper. Top with lemon slices.
Toss asparagus with remaining tablespoon oil, remaining 2 cloves minced garlic, and season with remaining salt and pepper. Arrange around salmon. Bake in preheated oven, 10 minutes. Remove from oven, toss asparagus, then sprinkle with parmesan. Return to oven and bake until salmon has cooked through, about 5-10 minutes longer. Cut salmon into portions and serve.