1. FOR THE SQUASH: Adjust oven rack to lowest position and heat oven to 425°F. Using sharp vegetable peeler or chefs knife, remove skin and fibrous threads from squash just below skin (peel until squash is completely orange with no white flesh remaining, roughly 1/8 inch deep). Halve squash lengthwise and scrape out seeds. Place squash, cut side down, on cutting board and slice crosswise 1/2 inch thick.

2. Toss squash with melted butter, salt, and pepper until evenly coated. Arrange squash on rimmed baking sheet in single layer. Roast squash until side touching sheet toward back of oven is well browned, 25 to 30 minutes. Rotate sheet and continue to bake until side touching sheet toward back of oven is well browned, 6 to 10 minutes. Remove squash from oven and use metal spatula to flip each piece. Continue to roast until squash is very tender and side touching sheet is browned, 10 to 15 minutes longer.

3. FOR THE TOPPING: While squash roasts, melt butter with hazelnuts in 8-inch skillet over medium-low heat. Cook, stirring frequently, until butter and hazelnuts are brown and fragrant, about 2 minutes. Immediately remove skillet from heat and stir in water (butter will foam and sizzle). Let cool for 1 minute; stir in lemon juice and salt.

4. Transfer squash to large serving platter. Drizzle butter mixture evenly over squash. Sprinkle with chives and serve.

Serves 4 to 6