Bring 2 cups of salted water to a boil in a medium saucepan. Add 1.5 cups uncooked pasta and 1 teaspoon salt, cover, and cook for about 10 minutes until al dente; drain and set aside.
While the pasta cooks, slice the chicken breasts into strips and chop the onion and bell pepper.
Heat 1 tablespoon olive oil in a skillet over medium-high heat. Add the chopped onion and bell pepper and sauté 1–2 minutes until softened.
Add the minced garlic and cook about 30 seconds until fragrant and lightly golden.
Add the chicken strips, 1/2 teaspoon salt, 1/2 teaspoon black pepper, and 1/2 teaspoon garlic powder; sauté until the chicken is browned and almost cooked through, about 4–5 minutes depending on thickness.
Pour in 1 cup marinara sauce, cover the skillet, and simmer 5 minutes to finish cooking the chicken and meld flavors.
Add the drained cooked pasta to the skillet and toss to combine. Stir in 1/2 cup mozzarella or Italian blend until melted; turn off the heat.
If desired, sprinkle with 1/4 cup Parmesan and place under a hot broiler briefly until bubbly and golden, then serve.
