In a medium bowl, whisk together the olive oil, lime juice, chopped cilantro, minced garlic, minced jalapeño (if using), cumin, chili powder, salt, and pepper.

Place the flank steak or skirt steak in a resealable plastic bag or a shallow dish. Pour the marinade over the steak, making sure it's evenly coated. Seal the bag or cover the dish and refrigerate for at least 30 minutes, or up to 4 hours.

Rinse the long-grain rice under cold water until the water runs clear.

In a medium saucepan, combine the rinsed rice, water or chicken broth, olive oil, and salt. Bring the mixture to a boil over high heat. Once boiling, reduce the heat to low, cover the pot, and simmer for 18-20 minutes, or until all the liquid is absorbed and the rice is tender. Do not lift the lid during cooking!

Remove the pot from the heat and let it sit, covered, for 5-10 minutes. Fluff the rice with a fork, then stir in the lime juice and chopped cilantro.

Preheat your grill to medium-high heat. Alternatively, heat a large skillet over medium-high heat on the stovetop.

Remove the steak from the marinade and discard the marinade. Grill or sear the steak for 3-5 minutes per side for medium-rare, or longer depending on your desired level of doneness. Use a meat thermometer to ensure the steak reaches your desired internal temperature.

Transfer the cooked steak to a cutting board and let it rest for at least 5 minutes before slicing. Slice the steak thinly against the grain.

Divide the cilantro lime rice among bowls. Top with the sliced steak, black beans, corn, avocado, tomatoes, red onion, shredded lettuce, sour cream or Greek yogurt, salsa, and a lime wedge.

Serve immediately and enjoy!