Thinly slice the onion and chop the tomatoes into slices; set aside.
In a pan, heat the oil and add the cumin seeds. Allow them to sizzle for a moment.
Once they are sizzling, add the tomatoes and cook for about 5-7 minutes.
Add the chicken and marinade into the pot and bring to a boil. Cover and allow to simmer over small/medium heat for 10 minutes till chicken is cooked.
Taste the curry and adjust seasoning where necessary. Enjoy and serve hot!