In a large bowl add ground beef, rice, egg, 2 teaspoons grated onion, tomato juice and 1 teaspoon salt.
Mix well and roll into 1-1/2" balls. Arrange in greased 9x13 casserole dish and set aside.
In large skillet, heat butter. Add 1/4 cup minced onion, celery and bell pepper. Saute until tender crisp. Remove from heat and add tomato soup, water, lemon juice, brown sugar, dry mustard and 1/2 teaspoon salt. Return to heat and simmer for five minutes, stirring often.
Pour sauce over meatballs, cover and bake at 350 degrees for 1-1/2 hours.