Preheat the oven to 425°F (220°C). Line a large sheet pan with parchment paper or lightly grease it.
In a large bowl, combine the halved baby potatoes, 2 tablespoons olive oil, garlic powder, onion powder, dried parsley, grated Parmesan cheese, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Toss until the potatoes are evenly coated.
Spread the seasoned potatoes in a single layer on one side of the prepared sheet pan.
Roast the potatoes in the preheated oven for 15 minutes.
While the potatoes begin roasting, prepare the honey mustard sauce by whisking together Dijon mustard, honey, mayonnaise, lemon juice, smoked paprika, 1/4 teaspoon salt, and 1/4 teaspoon black pepper in a small bowl until smooth.
After the potatoes have roasted for 15 minutes, remove the sheet pan from the oven. Push the potatoes to one side of the pan.
Place the salmon fillets on the empty side of the sheet pan, skin-side down if applicable.
Brush each salmon fillet generously with the honey mustard sauce.
Return the sheet pan to the oven and roast for an additional 10 minutes, or until the salmon is cooked through and flakes easily with a fork and the potatoes are tender and golden brown.
Remove from the oven and let rest for 2 minutes before serving.