Step 1: Preheat and Prep

• Preheat your oven to 400°F (200°C).
• Line a baking sheet with parchment paper or lightly grease it with olive oil.
• Arrange the sweet potato rounds in a single layer on the baking sheet. Drizzle with olive oil, and season generously with salt and black pepper.

Step 2: Roast the Sweet Potatoes

• Place the sweet potatoes in the preheated oven. Roast for 20-25 minutes, flipping halfway through to ensure even cooking. The edges should be golden brown and slightly crispy.

Step 3: Caramelize the Onions

• While the sweet potatoes are roasting, heat a skillet over medium-low heat. Add 1 tablespoon of butter and allow it to melt.
• Add the thinly sliced onions and a pinch of salt. Cook slowly, stirring occasionally, until the onions are golden brown and caramelized—about 20 minutes. Lower the heat if needed to prevent burning. Set aside once done.

Step 4: Prepare the Rosemary Butter

• In a small saucepan, melt the remaining 3 tablespoons of butter over medium heat. Add the minced garlic and chopped rosemary, stirring frequently until fragrant, about 2-3 minutes. Remove from heat and set aside.

Step 5: Assemble and Bake

• Once the sweet potatoes are roasted, remove them from the oven and transfer to a large baking dish.
• Layer the caramelized onions over the sweet potatoes, spreading them evenly.
• Sprinkle the freshly grated Parmesan cheese over the top.
• Drizzle the rosemary-infused butter evenly over the sweet potatoes and onions.

Step 6: Final Bake

• Return the baking dish to the oven and bake for an additional 10 minutes, or until the Parmesan is melted and golden brown.

Step 7: Serve and Garnish

• Remove from the oven and let it cool for a few minutes.
• Optionally, garnish with fresh chopped parsley and a light squeeze of lemon juice for added freshness.
• Serve warm.