Heat your grill on high for at least 10 minutes to get nice and hot.
Place your steak on a cutting board or ¼ sheet pan and pat dry with a paper towel. Sprinkle with cumin, garlic powder, salt, and pepper. Pour oil all over and use your hands to rub everything around to coat evenly.
Once the grill is hot enough, place the steak on the grill, cover, and cook for 2-4 minutes or until you have nice grill marks on the bottom. Flip and cook until it reaches your desired temperature, about 1-5 more minutes. Transfer it to a cutting board to rest for 10 minutes, then cut into bite-sized pieces
Meanwhile, add all dressing ingredients to a high-speed blender and blend until smooth and combined.
In a medium/large bowl, add the beans, scallions, remaining corn, and steak. Pour about ½ of the dressing over top and toss to coat.
Add the lettuce to your individual bowls and pour just a bit of dressing over and toss gently to coat. Scoop ¼ of the steak and bean salad over top. Drizzle each bowl with the remaining dressing along with plenty of feta, avocado, and black pepper.