Add the ground beef and onion to a large dutch oven over medium heat and cook until browned. Drain the grease.
Add the garlic to the pan and cook for 30 seconds, stirring constantly.
Stir in the tomato sauce, undrained canned tomatoes, and water. Add the Italian seasoning, salt, pepper, and sugar. Bring to a boil over medium heat.
Once boiling, break the spaghetti in half and add to the pot. Stir to submerge the noodles in the liquid.
Return to a boil, reduce to a simmer, and cover.
Cook, stirring occasionally, for 10-12 minutes or until noodles are cooked through.
Sprinkle the Parmesan cheese and parsley over the top and stir to combine.
Serve immediately.
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Notes
We break our spaghetti in half to be sure it's submerged in the sauce. You can skip this step, but you'll want to be sure you get those noodles covered in the liquid so they cook evenly. Taste the spaghetti before serving and stir in additional herbs and spices to add more flavor, if you like a more robust sauce.