Tear bread into small pieces, and place in a small shallow bowl. Add water to cover, and let soak about 5 minutes. Squeeze water from bread; discard water. Set bread aside.
Sauté onion in butter until tender. Combine sautéed onion, bread, meat, eggs, salt, nutmeg, parsley, lemon rind, lemon juice, and Worcestershire sauce in a large bowl. Mix well; shape into 2-inch meatballs.
Bring beef broth to a boil in a large Dutch oven; add meatballs. Reduce heat; cover and simmer 15 minutes. Remove meatballs; set aside. Reserve pan liquid.
Combine flour and water, mixing well. Stir flour mixture into reserved pan liquid. Cook over medium-high heat, stirring constantly, until thickened and bubbly.
Return meatballs to Dutch oven; cook over low heat until meatballs are thoroughly heated. Serve meatballs and gravy over hot cooked noodles.