Beef and Beer Stew

2 tablespoons butter
1 cup onion, sliced
2 pounds lean beef, cut into 1-inch cubes
1 tablespoon of flour
1 cup of beer
3 teaspoons vinegar
1 teaspoon of salt
1/2 teaspoon pepper
1/2 teaspoon sugar
1 bay leaf
1/4 teaspoon thyme, crumbled

Preheat oven to 350 degrees. In a Dutch oven over medium-high heat, melt butter and then brown onions. Remove onions from the pan. Add beef and brown. Sprinkle beef with flour. Add onions and remaining ingredients and stir well Cover tightly and bake for about 2 1/2 hours or until very tender.