Peel the butternut squash, cut it in half lengthwise, and scoop out the seeds. Cut the squash into 1-inch cubes for even roasting.
Place the squash cubes on a parchment-lined baking sheet. Drizzle with olive oil, then sprinkle with salt, black pepper, Herbes de Provence, and garlic powder. Toss until evenly coated and spread into a single layer.
Bake at 400°F for 25 to 35 minutes, flipping halfway through, until the squash is golden on the edges and fork-tender.
While the squash roasts, melt the unsalted butter in a small saucepan over medium heat. Cook until it foams, turns golden amber, and smells nutty. Remove from heat immediately.
Drizzle the warm brown butter over the roasted squash and gently toss to coat. Serve immediately while warm.
