While the chicken and broccoli are cooking, slice your onion and mushrooms and mince the garlic.
Also, cook pasta in salted water according to package directions, drain, and return it to the pot.
While that's going, also heat the butter in a large skillet over medium heat until melted. Add onion and saute for one minute, then stir in the garlic, parsley, crushed red pepper, and mushrooms and saute for seven minutes, stirring occasionally, until mushrooms are browned and softened.
Stir in the tomatoes and heat through.
You can also chop the cooked chicken and stir it into the pasta rather than leaving the tenders whole as I did here, and note that they will get cooked through on the sheet pan, even though they don't particularly brown. This pasta dish is not super "saucy" -- so, you can optionally add some of your own favorite sauce if you prefer yours more so.