In a small bowl, combine cumin, curry, paprika, oregano, cayenne pepper (if using), salt, and black pepper; stir until thoroughly incorporated.
Rub seasoning mixture all over chicken breasts.
Heat 2/3 oil in a non-stick pan or skillet over medium heat.
Cook the chicken breasts on each side until browned and mostly cooked through to an internal temperature of 150°F. (Cooking time will depend on the size of the chicken breasts.)
Remove chicken from the pan and set aside.
Add remaining olive oil to the pan; sauté the onions and garlic for 2-3 minutes. Add tomatoes and kale, sauté for 3-5 minutes, or until kale is wilted. Season with salt and pepper.
Stir in the coconut milk and return chicken breasts to the pan; reduce heat to medium-low and cook for 4-5 minutes, or until chicken is cooked through and the sauce has reduced and thickened. Chicken is done when internal temperature registers at 160˚F.
Taste sauce for salt and pepper; adjust accordingly.
Garnish with cilantro and serve.
Notes
Pro tips: Butterfly the chicken: Lay the breasts down on a cutting board, using a sharp knife parallel to the cutting board slice the breasts through the middle (carefully) all the way in half.