A method of resistance spot welding steel workpieces—at least one of which includes a high-strength steel substrate having a tensile strength of 1000 MPa or greater—involves passing a pulsating DC electrical current between a pair of aligned welding electrodes that are pressed against opposite sides of a workpiece stack-up that includes the steel workpieces. The pulsating DC electrical current delivers sufficient power through the weld site by way of electrical current pulses to initiate and grow a molten steel weld pool at each faying interface within the workpiece stack-up that solidifies into a weld nugget of uniform hardness. In other words, each of the weld nuggets formed by the pulsating DC electrical current does not include soft, coarse, and alloy deficient shell regions that tend to reduce the strength of the weld nugget.