Slow Cooker French Onion Soup

1/4 cup butter

4 large onions, thinly sliced

4 cups beef broth

1 clove garlic, minced

Salt and ground black pepper, to taste

Melt butter in a skillet over medium heat. Cook and stir onions in melted butter until clear and browned, 10 to 15 minutes; transfer to a slow cooker. Add beef broth, garlic, salt, and black pepper to the slow cooker.

Cook on High for 4 hours or on Low for 8 hours.