In a small bowl, whisk together the fajita marinade: 2 Tablespoons oil (vegetable or canola), 3 Tablespoons lemon juice, 1–2 cloves garlic (minced), 1 teaspoon ground cumin, 1 teaspoon garlic powder, 1 teaspoon onion powder, a pinch of salt, and freshly ground black pepper to taste.

Slice the 1 pound boneless skinless chicken breasts or tenders into bite-sized pieces or strips. Place the chicken in one large zip-top bag. Place the chopped 1 whole onion, 1 green bell pepper (chopped), and 1 red bell pepper (chopped) in a second large zip-top bag.

Pour half of the marinade into the bag with the chicken and the other half into the bag with the vegetables. Seal each bag and toss to coat. Refrigerate both bags for at least 15 minutes or up to a few hours.

When ready to cook, heat 1 Tablespoon olive oil in a large skillet over medium-high heat until hot.

Remove the chicken from its bag, discarding any remaining marinade in the bag. Add the chicken to the hot skillet and cook until browned and cooked through, about 3–5 minutes per side (total time will vary with piece size) or until the internal temperature reaches 165°F. Transfer the cooked chicken to a plate and tent with foil.

Add the marinated vegetables and the remaining 1–2 cloves garlic (minced) from the vegetable bag to the same skillet. Sauté until the onion and peppers are tender, about 4–5 minutes. Transfer the vegetables to the plate with the chicken.

Pour 2 cups low-sodium chicken broth and ½ cup milk into the skillet. Add the 14.5 ounce candiced tomatoes, undrained, 8 ounces penne pasta, and ½ teaspoon salt. Stir to combine and bring the mixture to a boil.

Once boiling, cover the skillet, reduce the heat to medium-low, and cook for 13–15 minutes, stirring occasionally, until the pasta is tender and most of the liquid is absorbed.

Return the cooked chicken and sautéed vegetables to the skillet. Stir to combine and heat through, about 1–2 minutes.

Serve immediately, topped with salsa and sour cream if desired.