Cut the chicken breasts into 2 inch pieces, then sprinkle the pieces evenly with 1 teaspoon of salt and the black pepper.
Pour the vegetable oil into a skillet over high heat. Once the oil is hot, cook the chicken until browned. Do not worry about cooking the chicken through. Brown it, then place to the side.
Lower heat to medium-high, then add the onion, ginger, and garlic. Cook, stirring often, until the onion turns translucent.
Add to the onion mix the curry powder, cayenne pepper, ground cumin, ground coriander, ground turmeric, and one tablespoon of water. Stir while heating for one minute.
Add in the crushed tomatoes, plain yogurt, cilantro and the last teaspoon of salt. Stir to combine.
Add the chicken back into the skillet, plus an additional 1/2 cup water. Stir the mix thoroughly, bring the mix to a boil, then lower heat and simmer, covered, for 20 to 25 minutes to cook the chicken through.
Uncover, check that the chicken is cooked through, then add the garam masala. cilantro, and lemon juice. Stir one last time, then serve over rice.