Bobby Flay's Sheet Pan Salmon with Roasted Potatoes and Creamy Meyer Lemon Dressing

I made this with yellow mustard instead of dijon and whole grain, and it was still very tasty. Lowering the temperature so low to cook the fish is a bit confusing to me, I ended up increasing it to 350 again as at 20 min it was not cooked yet. (I like to overcook fish though.)