In a small bowl, combine the spinach, cheese and sour cream; spread over steak to within 1/2 in. of edges. With the grain of the meat going from left to right, roll up jelly-roll style. Slice beef across the grain into eight slices.
Cut steak horizontally from a long side to within 1/2 in. of opposite side. Open meat so it lies flat; cover with plastic wrap. Flatten to 1/4-in. thickness. Remove plastic.
In a small bowl, combine the spinach, cheese and sour cream; spread over steak to within 1/2 in. of edges. With the grain of the meat going from left to right, roll up jelly-roll style. Slice beef across the grain into eight slices.
Transfer to an ungreased baking sheet. Sprinkle with salt and pepper. Broil 4-6 in. from the heat for 5-7 minutes on each side or until meat reaches desired doneness (for medium-rare, a thermometer should read 135°; medium, 140°; medium-well, 145°).