Preheat the oven to 425°F (220°C). Line a large rimmed baking sheet with parchment paper or lightly oil it; a hot oven and a prepared pan help create a crisp surface.

Wash and prepare the sweet potatoes. You can peel them if you prefer a smoother texture, but leaving the skins on adds texture and nutrients. Cut into 1-inch cubes or 1/2-inch thick wedges for a mix of crunchy edges and tender centers.

In a large mixing bowl, combine the olive oil, melted butter, brown sugar, ground cinnamon, smoked paprika, and kosher salt. Whisk until the sugar dissolves and the mixture is cohesive.

Add the cut sweet potatoes to the bowl and toss thoroughly to coat every piece with the glaze. Spread the pieces out in a single layer on the prepared baking sheet with some space between pieces — crowding will steam them instead of roasting.

Roast in the preheated oven for 25–30 minutes, flipping once halfway through. Check for a deep golden-brown color on edges and a tender center when pierced with a fork. If you want more caramelized edges, increase the oven to 450°F for the last 5 minutes while watching closely.

Remove the pan from the oven and immediately drizzle the apple cider vinegar or lemon juice over the hot sweet potatoes; toss gently to coat. The acidity will sizzle and brighten the caramelized glaze.

Taste and adjust seasoning with extra salt or freshly ground black pepper if needed. Sprinkle the chopped fresh parsley over the top for color and freshness.

Serve warm as a side dish to roasted meats, grilled vegetables, or as part of a holiday spread. Leftovers refrigerate well and can be reheated in the oven to re-crisp edges.