Preheat oven to 425℉. Lightly oil a baking sheet.
Place chicken on a baking sheet and rub with 1 tbsp. of oil. Bake until cooked through and interior reaches 165℉, 15-20 minutes.
While chicken cooks, in a medium saucepan heat remaining 1 tbsp. of oil over medium heat. Whisk in flour and chili powder and cook 1 minute. Whisk in broth and tomato sauce, bring to a gentle simmer, and cook, whisking occasionally, until slightly thickened, about 15 minutes.
Use two forks to shred chicken and toss in a medium-sized bowl with sauce. Serve with tortillas, and top with queso and green onion.