Begin by melting the butter in a medium saucepan over medium heat. Add the diced onion and sauté for about 3-4 minutes, or until the onion is translucent and fragrant.
Stir in the long grain white rice, ensuring each grain is coated with the buttery onion mixture. Sauté for another 1-2 minutes to toast the rice lightly.
Add the corn, garlic powder, cumin, and chili powder to the rice. Give everything a good stir to combine and let the spices bloom for a minute.
Pour in the chicken broth and the can of RO*TEL tomatoes with green chiles. Stir well and bring the mixture to a gentle boil.
Once boiling, reduce the heat to low, cover the saucepan, and let it simmer for about 18-20 minutes or until the rice is tender and has absorbed all the liquid.
Remove the saucepan from the heat and let it sit, covered, for another 5 minutes. Then, fluff the rice with a fork. Squeeze the juice of half a lime over the top and mix gently.
Finally, garnish your Southwest Rice with freshly chopped cilantro. Serve it warm as a side dish or as a base for your favorite proteins.