In a blender combine the onion, garlic, gingerroot, chili, lemon zest, and water and blend until pureed. In a casserole set over moderate heat, warm the oil until it is hot. Add the paste and cook it, stirring, for 3 minutes. Add the chicken, carrots, and salt to taste, and cook, turning the chicken until lightly colored on both sides, for about 10 minutes. Add the curry powder and cook, stirring and turning, for 5 minutes. Add the coconut milk and simmer, stirring occasionally, for about 10 minutes, or until chicken is cooked through. Stir in the lemon juice, to taste and the cilantro. Serve with rice.