1 pound boneless, skinless salmon fillet, cut into 4 pieces
1 pound green beans, trimmed
Preheat oven to 450 degrees. Whisk together honey, mustard, vinegar, and oil; season with salt and pepper. On a rimmed baking sheet, toss onion with 2 tablespoons vinaigrette and bake 5 minutes.
Meanwhile, stir 1 tablespoon vinaigrette into breadcrumbs. Coat fish with 1 tablespoon vinaigrette and season with salt and pepper; top with breadcrumb mixture and add to sheet. Bake until fish is cooked through, about 7 minutes.
In boiling salted water, cook green beans until crisp-tender, about 4 minutes; drain and toss with onion and 1 tablespoon vinaigrette. Refrigerate remaining vinaigrette in an airtight container for Chicken and Roasted Vegetable Salad. Serve fish with vegetables.