Oven & Spice Prep : Position a rack in the center of your oven and preheat to 400°F (200°C). In a small bowl, whisk together the onion powder, garlic powder, smoked paprika, ½ teaspoon of salt, ⅛ teaspoon of black pepper, and the optional cayenne pepper.
Season the Vegetables : In a large mixing bowl, combine the diced sweet potatoes and broccoli florets. Drizzle with the avocado oil and pour over the vegetable broth, which helps the vegetables steam and soften. Sprinkle with the remaining ½ teaspoon of salt and ⅛ teaspoon of black pepper. Toss everything thoroughly to ensure an even coating.
First Roast : Spread the seasoned vegetables in a single, even layer on the extra-large baking pan. Transfer to the preheated oven and roast for 20 minutes, stirring once halfway through, until the sweet potatoes begin to get tender.
Prepare Salmon & Sauce : While the vegetables are roasting, prepare the salmon. Rub each fillet on all sides with the prepared spice mixture. In a separate medium bowl, create the sauce by whisking together the Greek yogurt, lemon zest, lemon juice, fresh dill, and chives until smooth.
Combine and Finish Roasting : Remove the baking pan from the oven. Carefully clear six spaces among the vegetables and arrange the salmon fillets on the pan. Return the pan to the oven and roast for an additional 10-12 minutes. The dish is ready when the vegetables are fully tender and the salmon's internal temperature reaches 145°F (63°C) at its thickest point.
Garnish and Serve : Divide the roasted vegetables and salmon fillets among six plates. Drizzle generously with the dill-yogurt sauce and sprinkle with the crumbled goat cheese. Serve immediately.