Spray a medium (9-inch) skillet liberally with oil, or add a small amount of oil to the pan, and heat at medium-high temperature. Add onion and cook on medium, stirring occasionally, until translucent, about 4 to 5 minutes.
Add chicken, ginger, garlic and salt, and cook on high, stirring occasionally, until most of the liquid has evaporated and some bits of the chicken start to crisp, about 7 to 10 minutes.
Lower heat to medium and stir in cumin seeds, chile powder, coriander and turmeric. Add
tomatoes and continue cooking, stirring occasionally, until the tomatoes start to break down, about 5 minutes.
Add bell pepper and green chiles. Continue cooking on medium, stirring occasionally, until
the bell pepper starts to soften but still maintains some crunch, about 5 to 7 minutes.
Turn off the stove, then sprinkle with garam masala, lemon juice and fresh cilantro.