We computationally investigate the deformation of a closed bilayer membrane (vesicle) in a DC electric pulse with a goal of understanding cell electroporation. The electric stresses exerted on the area-incompressible interface generate non-uniform tension that can exceed the membrane lysis tension and drive pore opening. Using the two-dimensional boundary integral method, we track the spatial and temporal evolution of the highest membrane tension. Our simulations highlight the dynamic nature of electrotension and, in contrast to the common assumption, a possibility of electroporation away from the poles.