Spinach risotto

1. In 2-quart casserole, cook onion and olive oil on high 3-4 minutes, until tender, stirring halfway through cooking.
2. Stiri in rice, coating each grain.
3. Stir stock and salt into rice.
4. Cook, covered, on high 5-8 minutes, until boiling.
5. Stir. Cook, covered, on medium (50 % power) 13-15 minutes, until liquid is absorbed and rice is tender.
6. Drain spinach well, squeezing to remove all liquid.
7. Stir spinach, parmesan, and pepper into rice.
8. Let stand, covered, 5 minutes.
9. Remove seeds from tomato and cut into ½" chunks; stir into rice.