Preheat a grill pan or skillet over medium-high heat and lightly coat with a cooking spray or a small amount of olive oil if desired.
Season the chicken breast with chili powder, cumin, salt, and pepper.
Grill the chicken for 6-7 minutes per side or until fully cooked through, then allow it to rest before slicing or shredding.
While the chicken cooks, prepare the brown rice according to package instructions if not already cooked.
In a small bowl, mix the avocado, Greek yogurt, lime juice, chopped cilantro, and a pinch of salt and pepper to make the creamy dressing.
In a large bowl, combine the black beans, brown rice, chopped red bell pepper, diced red onion, and shredded romaine lettuce.
Slice or shred the cooked chicken and add it to the bowl.
Drizzle the creamy cilantro-lime dressing over the bowl and toss gently to combine all the flavors.
Serve immediately and enjoy your vibrant, spicy chicken taco bowl.