Preheat the oven to 375°F (190°C).

In a mixing bowl, combine the chicken, onion, potatoes, cumin, olive oil, and some salt. Transfer the mixture to a baking dish. Stir in the tomatoes and season with salt and pepper. Add just enough water to lightly coat the bottom of the dish (no need to submerge).

Cover the dish tightly with foil and bake for 50-60 minutes, stirring halfway, until the potatoes are tender and the chicken is cooked throughout the baking dish. Cooking time may vary.

Remove the foil, stir gently, and return to the oven. Bake uncovered for 10-20 minutes more, until the chicken is lightly golden and the potatoes develop some color.