Sauté the onions in the butter or oil 5 minutes or so, until tender and translucent; raise heat and sauté a few minutes longer, until lightly browned. Scrape into the mixing bowl.
Toss all the rest of the ingredients except for the bay leaves rather gently with the onions. Sauté a spoonful, and taste, carefully - if you are to serve the meat loaf cold, exaggerate a bit on the seasoning. Either form into a loaf shape on a buttered jelly-roll pan. Top with the bay leaves.
Preheat the oven to 350°F and set the meat loaf in the lower middle level.
Bake about 1-1/2 hours.
It is done when the juices run almost clear with a pale pink tinge, the meat is lightly springy to the touch. A meat thermometer should read 155°F - do not remove the thermometer until the meat rests before serving time, or the juices will burst out.
Let cool for 30 minutes. Pour off fat and juices. Transfer the loaf to a board or platter. Serve hot with salsa , or tomato sauce.