1/4 teaspoon salt (or as per taste)
2 teaspoons olive oil
1 pound skinless, boneless chicken breasts
1 large red onion, halved and thinly sliced
4 cloves garlic, finely chopped
2 green bell peppers, cut into thin strips
1-1/2 cups canned crushed tomatoes
1 tablespoon unsweetened cocoa powder
2 teaspoons packed light brown sugar
2 teaspoons red wine vinegar
1/2 teaspoon cinnamon
In large skillet, heat oil over medium heat. Add chicken and cook 2 minutes per side until golden brown. Remove with a slotted spoon. Add onion and garlic and cook 7 minutes, stirring frequently, until onion is tender. Add peppers and cook 5 minutes. or until softened.
Stir in salt, tomatoes, 2/3 cup of water, cocoa powder, brown sugar, vinegar, and cinnamon. Bring to a boil, add chicken, and reduce to a simmer. Cover and cook 10 minutes. Uncover and cook 3 to 5 minutes, stirring occasionally, until chicken is cooked through and sauce is lightly thickened.
Transfer chicken to a cutting board, thinly slice, and spoon chicken and sauce over rice and serve.