Preheat oven to 400 degrees. Place poblano peppers on a baking sheet and roast for 15 minutes. Flip the peppers over and roast 10 more minutes.
Place the peppers into a bowl and cover with plastic wrap for 5 minutes. Then, peel, seed and chop.
Reduce the oven temperature to 375 degrees.
Combine 1 Tbsp. olive oil with the smoked paprika, garlic powder, onion powder, cumin, cayenne pepper and salt. Toss the chicken in the seasonings.
Transfer chicken to a baking dish and roastfor 20 minutes.
While the chicken is roasting, caramelize the onions: Combine the sliced onions with 1 Tbsp. of olive oil in a large skillet over medium heat. Season with salt and pepper as the onions cook down and become a deep golden brown color, about 20 minutes.
Remove the chicken from the oven. Flip. Top each chicken breast with caramelized onions, chopped peppers, tomatoes and one slice of cheese. Return to the oven for 10 more minutes.
Before serving, garnish with sliced avocado, crumbled Cotija cheese and chopped fresh cilantro, if desired.