Add the butter, minced garlic, and crushed red pepper flakes to a large skillet and saute on low-to-medium heat until the garlic in softened.

Prepare the penne pasta by following the directions on the package.

Add in the mushrooms to the skillet with the garlic and allow them to simmer for 5-10 minutes with a lid on or until they start to release their moisture. Add in the fresh spinach, marinara sauce, tomato, greek yogurt, and pasta. Mix together. Add salt and pepper, to taste.