Cook the rice or grain according to package directions. Spread it on a sheet pan to cool completely so it stays fluffy instead of clumping when you assemble the bowls.

Pat the chicken dry with paper towels and season both sides with cumin, chili powder, garlic powder, salt, and pepper. Heat a large skillet over medium-high heat with a thin layer of oil, then add the chicken and cook without moving it for 5 to 7 minutes per side until the internal temperature reaches 165°F.

Remove the chicken from the pan and let it rest for 5 minutes. While it rests, toss the bell peppers, corn, and red onion in the same skillet over high heat for 4 to 5 minutes until charred in spots but still crisp.

Slice the chicken into strips. Rinse the black beans and drain them well.

Assemble the bowls by layering rice, sliced chicken, roasted vegetables, and black beans. Top with fresh cilantro, a squeeze of lime, avocado slices, salsa, and sour cream or Greek yogurt.