Cut the chicken breast into bite-sized pieces.
Finely chop the onion and tomato.
Add olive oil to a pan and sauté the onion.
Add the chicken breast and cook.
Add tomatoes and sauté together.
Add rice and stir-fry for 2-3 minutes.
Pour in chicken stock or water and bring to a boil.
Simmer over medium-low heat, stirring, until the rice is cooked.
Season with salt and pepper.
Serve in a bowl and sprinkle with Parmesan cheese.