Recipe courtesy of Judy's Kitchen (http://judyskitchen.blogspot.com)
Rating:  9.5 out of 10

3 Tbsp. extra-virgin olive oil, divided use

1 medium sweet onion, finely chopped (about 1 cup)

2 tsp. balsamic vinegar

1/8 tsp.+ 3/4 tsp.  fine sea salt or Diamond kosher salt, divided use

tiny pinch + 1/8 tsp. of white pepper, divided use (you can also use black, if preferred) 

2 Tbsp. finely chopped fresh parsley

1 Tbsp. ketchup

1 Tbsp. drinking-quality red wine (I used Cabernet Sauvignon) 

1 lb. organic grass-fed ground beef

In 9- or 10-inch skillet, heat 1 Tbsp. oil and onion over medium heat till onions are transparent, about 5 minutes.  Stir in vinegar, 1/8 tsp. salt and tiny pinch of pepper.  Cover and reduce heat to low.  Cook for 35-40 minutes, till onions are reduced and caramelized, checking occasionally and stirring to be sure they are not sticking.   Cool completely.

In rectangular or square pan, combine cooled onions, parsley, ketchup, wine, and remaining 2 Tbsp. oil.  Stir well with fork.  Top mixture with pieces of ground beef.  Sprinkle the beef with the remaining 3/4 tsp. salt and 1/8 tsp. of pepper.  Mix lightly but thoroughly with hands or two forks.  Separate into 4 equal pieces, each weighing approximately 4.8 oz. each.  With wet hands, roll each between palms to form a ball, then flatten lightly with fingers to form patties about 1/2 – 3/4” thick.  If desired, sprinkle each lightly with additional salt and pepper before placing on hot grill (450F).  Grill about 3 minutes each side, then transfer to platter to rest 5 minutes.  Burgers should be pink in centers after resting.