Heat the olive oil in a large pot over medium heat. Add the chopped onion and cook, stirring occasionally, until translucent and soft, about 5 minutes.
Stir in the minced garlic and cook for 1 minute until fragrant, being careful not to let it burn.
Add the diced tomatoes, tomato paste, and tomato sauce to the pot. Stir well to combine.
Mix in the dried basil, dried oregano, salt, black pepper, and sugar. Bring the sauce to a gentle boil, then reduce the heat to low. Simmer uncovered for 30 minutes, stirring occasionally, until the sauce thickens.
Stir in the fresh parsley during the last 5 minutes of cooking. Taste and adjust seasoning if needed.
While the sauce simmers, prepare your canning jars, lids, and boiling water bath according to safe canning practices.
Carefully ladle the hot sauce into sterilized jars, leaving 1/2 inch of headspace. Wipe the jar rims clean, place the lids on, and tighten the bands fingertip-tight.
Process the jars in a boiling water bath for 35 minutes. Remove and let cool completely before checking the seals and storing.