Step 1

Bring a large pot of heavily salted water to a boil over high heat. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 475°F.

Step 2

Halve 2 pounds baby or fingerling potatoes. Add the potatoes to the boiling water and cook until fork tender, 10 to 15 minutes. Meanwhile, pick the leaves from 1 fresh rosemary sprig and finely chop (about 1 tablespoon) and place in a small bowl (if using dried rosemary, place 1 teaspoon in the bowl). Add 1 tablespoon olive oil, 1 teaspoon kosher salt, 1/2 teaspoon black pepper, 1/2 teaspoon garlic powder, and 1/4 teaspoon cayenne if using.

Step 3

Drain the potatoes and run under cool water; let sit in the strainer. Melt 2 tablespoons unsalted butter in the now-empty pot over medium heat (dry the pot first if needed). Remove the pot from the heat, add the rosemary mixture, and whisk to combine.

Step 4

Add the potatoes and toss until evenly coated in the butter mixture. Transfer to a rimmed baking sheet and arrange in a single layer cut-side down.

Step 5

Roast until the cut sides of the potatoes are golden brown, 20 to 25 minutes. Flip the potatoes over and roast until crisp, about 15 minutes more.