- 1 large yellow onion, finely chopped (about 1 cup)
- 1 tablespoon olive oil
- 1 tablespoon unsalted butter
- ½ teaspoon apple cider vinegar
- 2 eggs, beaten
- 1 8 ounce can tomato sauce
- ½ cup milk
- 1 cup dry breadcrumbs
- 1 ½ teaspoon salt
- 2 teaspoons freshly ground black pepper
- 1 tablespoon dry mustard
- 1 ½ pounds ground venison or lean ground beef
- 2 cloves garlic, minced (about 1 teaspoon)
- Heat the olive oil and butter together in a large heavy skillet over medium heat until the butter is melted. Add the onion to the skillet and cook slowly until the onion is caramel-colored, stirring often, 30 to 40 minutes. Carefully add the vinegar to the onion, stirring to deglaze the skillet. Remove the caramelized onion from the heat.
- Preheat the oven to 350 degrees.
- Combine the eggs, tomato sauce, milk, breadcrumbs, salt, pepper, and dry mustard in a large bowl. Stir well to combine thoroughly. Add the venison or beef, garlic, and caramelized onion, working well with your hands to combine thoroughly. Press the meat mixture into an ungreased 9 x 5 x 3 loaf pan. Bake, uncovered, for 70 minutes.
- Allow the meatloaf to rest 10 minutes before slicing and serving.