A post-tensioned tube foundation for supporting a structure subject to high upset forces is described herein. The post-tensioned tube foundation includes an outer CMP positioned within an excavated hole. A foundation plug is positioned within the cavity of the outer CMP and extends across the bottom of the excavated hole. An inner CMP is positioned within the cavity of the outer CMP such that an annular space is defined between the inner CMP and the outer CMP. A tubular concrete base is positioned within the gap defined between the inner CMP and the outer CMP. A void forming element is positioned within the gap defined between the inner CMP and adjacent the top surface of the foundation plug.