Using a small paring knife, carefully carve a jack-o'-lantern face on the side of each bell pepper. Remove the tops, seeds, and membranes, retaining the tops for later.
Evenly spoon the beef mixture into each prepared pepper and replace the removed tops.
Right before serving, remove the tops and sprinkle with parsley, then put the tops back on. Warm the remaining tomato sauce and serve it spooned around each pepper.