Method
In a large bowl, toss the chicken pieces with lemon juice, salt, and pepper to coat. Set aside.
Heat oil in a large, heavy saucepan over medium heat. Stir in cumin seed and cook 1 minute, until lightly toasted. Mix in onion, garlic, and ginger. Cook until onion is tender. Add tomatoes, and season with chili powder, turmeric, garam masala, ground cumin, coriander, and paprika. Continue to cook and stir 2 minutes.
Mix yogurt into the saucepan until well blended. Add chicken pieces, and potatoes. Mix in water and tomato juice. Reduce heat to medium-low. Cover and simmer about 40 minutes. Adjust seasonings to taste and garnish with fresh cilantro before serving.