1. Heat the oven to 450°. In a roasting pan, combine the carrots with the oil, cumin, 1/4 teaspoon salt, and the pepper. Roast the carrots, stirring occasionally, until tender and browned, about 20 minutes.
2. In a food processor, puree the carrots with the butter, milk, lemon juice, and 1/8 teaspoon salt. If necessary, reheat the puree in a small saucepan over low heat, stirring.