This letter introduces a computationally efficient inversion algorithm based on the contrast source inversion method for two-layered media applications. The proposed algorithm employs Cauchy data to derive an integral representation of the electromagnetic field inside the homogeneous neighborhood of the target. This representation yields a Lippmann-Schwinger-type integral equation that does not involve the background Green's function. Therefore, it provides a significant improvement in computational efficiency. Numerical experiments are provided to demonstrate the performance of the method.