Bring a large pot of generously salted water to a boil. Cook the pasta until just al dente according to the package directions, reserve about 1/2 cup pasta water, and drain.

Cut the chicken into bite-size pieces, or pound chicken breasts to an even thickness and slice them after cooking. Season with about half of the Italian seasoning, the kosher salt, and black pepper.

Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Cook the chicken for approximately 4 to 6 minutes, turning occasionally, until browned and cooked through, then transfer it to a plate.

Add the remaining olive oil to the skillet. Cook the onion and bell pepper for 3 to 4 minutes until beginning to soften, then add the garlic and cook for 30 to 60 seconds.

Stir in the diced tomatoes with their juices, chicken broth, remaining Italian seasoning, and optional red pepper flakes. Simmer for 5 to 7 minutes so the sauce slightly reduces.

Return the chicken to the skillet and add the drained pasta. Toss until coated, adding reserved pasta water a tablespoon or two at a time if the sauce is too thick.

Remove the skillet from the heat or reduce it to low. Stir in or sprinkle with Parmesan and fresh herbs, then serve immediately.