Heat the oil in a large saucepan over medium-high heat. Add the onion and garlic and cook, stirring, for 3-4 minutes or until onion softens. Add the chicken and cook, stirring occasionally, for 3-4 minutes or until brown all over. Add the cumin, paprika and saffron and cook, stirring, for 1 minute or until aromatic. Add the rice, tomatoes and chicken stock, and bring to the boil. Reduce heat to low and cook, covered, for 15 minutes or until chicken and rice are tender.
Add the tomato paste, peppers and parsley, and cook, stirring, for 2-3 minutes or until heated through. Remove from heat. Divide the arroz con pollo among serving bowls and serve immediately.