Clean, wash and drain salads well. Cut romaine lettuce into strips. Wash and quarter tomatoes. Peel 1 orange so that the white skin is completely removed. Halve the orange lengthwise and cut into slices.
Squeeze the rest of the orange. Peel garlic and cut into slices. Wash the rosemary, pluck off the needles and chop roughly. Chop nuts coarsely.
Pat the lamb filet dry. Fry in 1 tbsp. hot oil all around for approx. 5 minutes. Fry garlic and rosemary briefly. Season. Remove the fillet.
Heat 1 tablespoon of oil in the frying fat. Roast the nuts in it. Deglaze with orange juice and vinegar. Season with salt, pepper and some sugar. Fold in 2-3 tbsp. nut oil. Cut the lamb filet into slices. Mix the salad ingredients with the marinade.
Arrange the fillet on top.