Cut the chicken breast into bite-sized pieces.
Finely chop the onion, garlic, and tomato.
Heat olive oil in a pan and sauté the garlic.
Add the chicken breast and onion, and cook until done.
Add the tomato and stir-fry together.
Pour in the tomato sauce and water, then bring to a boil.
Season with salt and black pepper.
Simmer on low heat until thickened.