In large skillet over medium-high heat, sauté rice mix with butter until golden brown. Add water, salsa and box seasonings; bring to boil. Reduce heat to low.
Cover, simmer 15 to 20 minutes or until rice is tender. Stir in beans and corn, let stand 5 minutes before serving.
Serve in tortillas with cheese and sour cream, if desired.
Servings: