Start by marinating the chicken. In a bowl, combine the chicken cubes with 1 teaspoon of olive oil, taco seasoning, garlic powder, cumin, kosher salt, chili powder, paprika, and oregano. Toss everything well to ensure the chicken is coated evenly. Let it sit for about 15 minutes to absorb the flavors.
While the chicken is marinating, take this time to prepare your vegetables. Dice the red onion, poblano pepper, and roma tomato. Mince the cilantro and set everything aside.
In a large skillet, heat the remaining 1 teaspoon of olive oil over medium-high heat. Once hot, add the marinated chicken to the skillet. Cook for about 5-7 minutes, stirring occasionally, until the chicken is golden brown and cooked through.
Once the chicken is cooked, add the diced red onion and poblano pepper to the skillet. Sauté for about 3-4 minutes until the vegetables are tender. Then, stir in the diced roma tomato and corn kernels, cooking for an additional 2 minutes. Remove from heat.
In serving bowls, layer the heated brown rice (or cauliflower rice) first. Top with the chicken and vegetable mixture. Sprinkle with cheddar-jack cheese and a dollop of sour cream or Greek yogurt if desired. Finish with a squeeze of fresh lime juice and garnish with extra cilantro.