The main aspect of Foveon is wide rich tonality and natural contrast. So if you open X3F file in Lightroom and set all parameters to zeroed, the image looks natural without stretching it from flat raw. If you do this with RAW from typical Bayer chip camera, the image is flat, low contrast, mainly midtones, weak colours. You have to add brightness and contrast, modify contrast curve to darks and highlights. Than the image looks good, but tonal range stays the same, it´s just stretched, skipping some tonal transitions.
Here I posted some characteristic Foveon photos: