1 can diced tomatoes (or you can be like me and realize 5 minutes before you are making dinner that you are somehow out of diced tomatoes and use whole instead, coring/dicing on your own :)
1 small onion, diced
2-3 cloves garlic, minced
Balsamic vinegar (about 3 Tbsp maybe?)
Basil (fresh is best but dried works)
Salt and pepper
In the same pan you cooked the tenderloin, add the onions to saute until translucent (add more oil if necessary). Add garlic and saute until fragrant, about 30 seconds.
Deglaze the pan with the balsamic vinegar.
Stir in tomatoes and basil, salt and pepper to taste, and simmer (for as long as you want, really). Spoon over the pork tenderloin milanese
Pairs Well With