Marinate the Steak: In a bowl, whisk together olive oil, balsamic vinegar, minced garlic, smoked paprika, chili powder, salt, and pepper. Place the flank steak in a resealable bag or shallow dish and pour the marinade over it. Ensure the steak is fully coated. Marinate in the refrigerator for at least 30 minutes, or up to 4 hours.

Cook the Rice: In a medium saucepan, combine rice, water, and salt. Bring to a boil, then reduce heat to low, cover, and simmer for 18-20 minutes, or until the rice is cooked through and the water is absorbed. Fluff with a fork.

Prepare the Black Beans: In a bowl, combine rinsed and drained black beans, chopped red onion, lime juice, cumin, salt, and pepper. Mix well.

Prepare the Corn Salsa: In a bowl, combine corn kernels, diced red bell pepper, chopped red onion, minced jalapeño (if using), chopped cilantro, lime juice, salt, and pepper. Mix well.

Prepare the Avocado Crema: In a blender or food processor, combine avocado, sour cream (or Greek yogurt), lime juice, water, salt, and pepper. Blend until smooth and creamy. Add more water if needed to reach desired consistency.

Grill the Steak: Preheat your grill to high heat. Remove the steak from the marinade and pat it dry with paper towels. This is crucial for getting a good sear. Grill the steak for 3-4 minutes per side for medium-rare, or longer depending on your desired level of doneness. Use a meat thermometer to ensure accuracy (130-135°F for medium-rare).

Rest and Slice the Steak: Remove the steak from the grill and let it rest for at least 10 minutes before slicing against the grain. This allows the juices to redistribute, resulting in a more tender and flavorful steak.

Assemble the Bowls: Divide the rice among bowls. Top with sliced steak, black beans, corn salsa, and avocado crema. Garnish with shredded cheese, chopped cilantro, and lime wedges, if desired.

Serve: Enjoy your delicious and healthy Grilled Steak Bowl!