Remove salmon from the fridge and let stand at room temperature while you prepare the potatoes.
Preheat oven to 400 degrees Fahrenheit. Line a large baking sheet with non-bleached parchment paper.
Wash potatoes and slice each one in half. Place all in a bowl.
Toss potatoes with olive oil, salt, and black pepper.
Arrange potatoes on a baking sheet and roast for 15 minutes in preheated oven.
In the meantime, mix Dijon mustard, lemon juice, minced garlic, butter, salt, and black pepper in a small bowl.
Push the potatoes to the sides of the baking sheet and place salmon fillets in the middle.
Brush the Dijon mixture over salmon. Any leftover can be poured over the potatoes.
Place the sheet pan back in the oven and bake for 8 to 10 minutes or until salmon reaches 145 degrees Fahrenheit. Do not overcook.
Remove from oven, plate, and serve.
