Cook noodles according to box directions, drain and set aside.
Season steak on both sides with the salt, pepper and first teaspoon of garlic powder. Heat the tablespoon of olive oil in a skillet and sear steak on both sides for 4 minutes each (or more depending on desired temperature). Set aside.
Melt the butter in the same skillet on a lower heat setting. Whisk in the flour til smooth, taking care not to allow clumps to form. Pour in the milk and then add the garlic powder, stir, and allow to simmer until thickened -- at least five minutes.
Add the parmesan and the tomatoes, then cover and allow to simmer another couple of minutes.
Add the pasta and stir to coat, then add the spinach and cover the skillet. Allow a couple minutes for the spinach to wilt, then stir.
Slice the steak and add to the pasta before serving. Drizzle with balsamic glaze and top with the chopped parsley if using.