Place chicken in bowl with curry powder, ground chile, and vinegar. Mix well with hands and set aside for 30 minutes, or marinate the chicken overnight for optimum results.
In a large pot, heat oil over medium-high heat until it shimmers. Once hot, add onions, garlic, ginger, curry leaves, lemon grass, cardamoms, cloves, and cinnamon. Fry, stirring frequently, until onions are golden brown.
Add chicken pieces one by one, stirring occasionally until chicken is browned. Add a little water to the bowl that contained chicken and slosh around to catch any remaining marinade and add to pot.
Stir in coconut milk and salt and bring to a boil. Reduce heat, cover and simmer for about 20 minutes. Stir in tomato paste and simmer for additional 10 minutes, then taste again for seasoning and serve.