Spaghetti sauce too sweet Trying to make spaghetti sauce and this is too sweet:

2 each 28 oz can crushed tomatoes (low salt)
8 oz can tomato paste
1 red onion diced
1 tablespoon dried oregano
1 teaspoon dried basil
1 teaspoon black pepper
4 garlic cloves
1 lb 97% fat free beef   

Brown the beef and simmer everything for 3-4 hours.

It just comes out too sweet. 

Salt and sausage (fat) would make it less sweet but also less healthy.  

I am thinking about poblano peppers and / or cilantro.

How to make this spaghetti sauce less sweet, without adding fat or salt?
The tomato paste in your recipe is a large contributor to the sweetness. You could reduce the amount you are using or substitute with tomato sauce. 

The addition of an acid would also help balance the sweetness. A splash of vinegar or wine for example.