Bring stock to the boil in a medium saucepan over high heat. Add peas, tomato and salt. Bring back to the boil. Add rice and stir. Cover. Lower heat to a bare simmer. Cook just until liquid is absorbed and rice is tender, about 15 minutes.
Remove saucepan from heat. Leave rice mixture to stand, covered, for 10 minutes. Uncover. Fluff up with a fork.