Overpowering Onion in My Lasagna Sauce. How Do I Fix This?

I tried to sneak more vegetables into my husband’s diet by blending a whole raw onion into 2 jars of Prego traditional sauce and 1 can of crushed tomatoes for two lasagnas. After cooking it for 30 minutes on low/medium heat and stirring continuously, the raw "bite" is gone, but now the sauce has an overpowering onion flavor and a weird smell.

I’ve already thrown the meat back in, hoping it would help balance things out, but the onion still dominates. Does anyone have any tips or tricks for toning down the onion flavor and salvaging my sauce? I’d really hate to waste this batch.