Heat your oven to 400 degrees Fahrenheit.
Combine the chili powder, paprika, onion powder, garlic powder, cumin, cayenne pepper, sugar, and salt in a small bowl and stir well.
Slice the onions and bell peppers into thin, 1/4-inch strips, and cut the chicken breasts into thin strips as well.
Place the chicken and sliced vegetables on a large baking sheet or dish.
Pour the cooking oil evenly over everything and sprinkle the prepared seasoning mix on top; toss thoroughly using your hands to coat each piece.
Spread the chicken and veggies in an even layer on the pan.
Roast in the oven for about 35 to 40 minutes, stirring once around halfway through baking.
When out of the oven, squeeze juice from half the lime over the chicken and vegetables.
To serve, spoon some of the cooked mixture onto a tortilla, then add cilantro sprigs and a dollop of sour cream if you like, finishing with an extra squeeze of lime juice.