In a small mixing bowl, combine the salt, black pepper, onion powder, and garlic powder to create the spice rub.
Season the diced chicken breasts thoroughly with the prepared spice rub.
Heat 2 tablespoons of olive oil in a large sauté pan over medium-high heat.
Add the seasoned chicken to the pan and sear until cooked through and golden brown, then remove and set aside.
In the same pan, add the remaining tablespoon of olive oil and sauté the finely chopped onion until translucent.
Stir in the minced garlic and cook for about 1 minute until fragrant.
Pour in the chicken broth, scraping up any browned bits from the bottom of the pan.
Return the chicken to the pan and add the cooked brown rice and the drained broccoli.
Stir everything together until well combined and heated through.
Fold in the Parmesan cheese and shredded sharp cheddar cheese until melted and creamy.
Serve immediately while warm.