Chicken Curry in a Hurry

1 ½ T olive oil
1 small yellow onion, thinly sliced
2 t curry powder
½ cup plain yogurt
¾ heavy cream
½ t kosher salt
¼ t black pepper
1 14.5 oz can diced tomatoes, drained (optional)
1 rotisserie chicken
2 cups cooked white rice (optional)
¼ fresh cilantro leaves, roughly chopped

Heat the oil in a large skillet over medium-low heat. Add the onion and cook, stirring occasionally, for seven minutes. Sprinkle with the curry powder and cook, stirring for one minute. Add the yogurt and cream and simmer gently for three minutes. Stir in the salt, pepper, and tomatoes (if using). Remove from heat. Slice or shred the chicken, discarding the skin and bones. Divide the rice (if using) and chicken among individual bowls, spoon the sauce over the top, and sprinkle with the cilantro.