Place chicken, breast side up, in a shallow roasting pan. Rub entire surface of chicken halves with lemon, squeezing out juice occasionally. Combine salt, pepper, and paprika; sprinkle over chicken. Brush chicken with 1/4 cup butter; sprinkle with sugar. Bake, uncovered, at 450° for 10 minutes. Baste with remaining butter. Reduce heat to 350°; cover and bake an additional 35 minutes or until tender.