We demonstrate a method for full and unambiguous temporal characterization of few-cycle electromagnetic pulses, including retrieval of the carrier envelope phase (CEP), in which the interference between non-linear frequency mixing components is spectrally resolved using Frequency Resolved Optical Gating (FROG). We term this process Real-Domain FROG (ReD-FROG) and demonstrate its capabilities through the complete measurement of the temporal profile of a single-cycle THz pulse. When applied at THz frequencies ReD-FROG overcomes the bandwidth limitations relating probe and test pulses in Electro-Optic (EO) sampling. The approach can however be extended generally to any frequency range and we provide a conceptual demonstration of the CEP retrieval of few-cycle optical field.