PreparationRoast potatoes: Put a 4-sided sheet pan in lower third of oven and preheat oven to 450°F. Stir cumin, oregano, and 3/4 teaspoon salt into oil in a large bowl. Add potatoes and toss. Arrange potatoes, cut sides down, in 1 layer in hot pan and roast, turning once, until golden, about 40 minutes. Meanwhile, make mayonnaise: Stir together mayonnaise, sour cream, cilantro, lime zest and juice, and 1/4 teaspoon salt in a small serving bowl. Serve potatoes with mayonnaise.
PreparationRoast potatoes: Put a 4-sided sheet pan in lower third of oven and preheat oven to 450°F. Stir cumin, oregano, and 3/4 teaspoon salt into oil in a large bowl. Add potatoes and toss. Arrange potatoes, cut sides down, in 1 layer in hot pan and roast, turning once, until golden, about 40 minutes. Meanwhile, make mayonnaise: Stir together mayonnaise, sour cream, cilantro, lime zest and juice, and 1/4 teaspoon salt in a small serving bowl. Serve potatoes with mayonnaise.