Remove the pork tenderloin from the refrigerator in time so the meat can come to room temperature. Carefully pat the meat dry with kitchen paper. Have the cauliflower rice and fresh spinach ready within reach.
Heat a generous amount of coconut oil in a spacious frying pan over medium-high heat. Place the pork tenderloin in the pan once the oil is fully melted and hot. Brown the meat on all sides in about five to eight minutes, then remove the pork tenderloin from the pan, loosely cover it with aluminum foil and let it rest outside the pan.
Place the same pan with the remaining cooking fat directly back on the heat. Add the cauliflower rice and stir-fry for about two minutes. Then add the spinach in portions, continuously stirring the mixture. Continue heating until the spinach has just wilted and the cauliflower rice is thoroughly hot.
Slice the rested pork tenderloin with a sharp knife into equal slices. Divide the warm stir-fry mixture of cauliflower rice and spinach over a plate. Place the sliced pork tenderloin on top and serve immediately.