Spanish Rice (microwave recipe)

This is so moist and yummy! My husband doesn't usually eat Spanish rice, but he really likes this recipe.

1 large onion, chopped
2 tablespoons butter
1 16-ounce can tomatoes, chopped and drained (reserve liquid)
1 cup long grain rice
1 1/2 teaspoon salt
2 teaspoons chili powder
1/8 teaspoon pepper
1/2 cup chopped green pepper
water

In 2-quart casserole combine onion, green pepper, and butter. Cook on high power for 2 1/2 minutes (in microwave). Stir once. Add enough water to reserved tomato liquid to equal 2 cups. Add to dish with tomatoes, rice, salt, pepper and chili powder. Cook covered on high power for 5 minutes and at medium power for 18 minutes. Stir once. Let stand covered for 5 minutes.