The Mishna states that one may not roast the Pesach on a grill. It then quotes an incident in which Rabban Gamliel instructed his servant to roast the Pesach on a grill. The Gemara asks: Was an incident cited to contradict what was previously stated?
The Gemara answers that the Mishna is incomplete and really discusses two types of “grills”. Do not roast it in a regular “grill”, do roast it in a perforated grill. With regard to this Rabbi Tzadok cited the incident with Rabban Gamliel, who roasted the Pesach lamb on a perforated grill.
What is a perforated “grill” and why is it better?
Rashi explains it refers to a “grill” with so much space between the beams, that the lamb doesn’t touch the metal at all. So it is fire-roasted and not metal-roasted.
This is a stretch of the wording; perforated refers to holes within a larger object, not space between beams. A “grill”, presumably means a grate. In addition, it is difficult to understand why this is a Chiddush; why would one have thought that it may not be used?
The Rambam states that a grill that is perforated in a way that the fire affects it, is permitted. He seems to learn that we are indeed talking about a grate. Some explain that here, the heat of the fire goes around the metal and therefore, considered fire-roasted and not metal-roasted.