Heat oil in a large skillet over medium-high heat.
Add onion and cook for 3 to 5 minutes, or until tender.
Add undrained tomatoes, water, tomato sauce, pasta and garlic salt; stir to combine and bring to a boil.
Cover; reduce heat and cook for 12 minutes or until pasta is almost tender.
In the meantime, heat bacon in microwave according to package directions.
Chop bacon; set aside.
Remove cover from skillet and add spinach on top of pasta mixture.
Cover; cook for 2 to 3 minutes, or until spinach wilts and pasta is tender.
Add bacon; stir to combine.
Serve with Parmesan cheese, if desired.