Preheat the oven to 400 degrees F (200 degrees C). Line a baking sheet with parchment paper.

Fill a large pot with lightly salted water and bring to a rolling boil. Cook penne in boiling water, stirring occasionally, until tender yet firm to the bite, about 11 minutes. Drain.

Add beaten egg whites to a shallow bowl. Place 2 cups Parmesan cheese into a second shallow bowl.

Dip chicken into egg whites and press into Parmesan cheese to coat both sides. Gently toss between your hands, so excess cheese falls away. Place coated chicken on the prepared baking sheet.

Bake chicken in the preheated oven until no longer pink in the center and the juices run clear, about 18 minutes.

Meanwhile, heat Alfredo sauce, diced tomatoes, tomato sauce, and red pepper flakes in a large saucepan over low heat. Allow sauce to simmer.

Heat a large skillet over medium-high heat; cook and stir mushrooms and spinach in the skillet until mushrooms are tender, about 5 minutes.

Stir cooked vegetables into the sauce.