Talmud: Shabbat 36

(continued from Previous comment, Hit character limit).
On top of this there is a general difference between How we cook nowadays with modern stove tops verses ovens from back in the day. Back then People were constantly stoking the coals and tending to the fire even if they were not involved in the cooking process. We Have a proof for this in Machalei Akum where the Rama writes that if you find food on the store and you are not sure who placed it there it is okay. One of the reasons mentioned is that Most Likely someone from the house did not stoke the coals at some point and thereby negated the Machalei Akum Issur even if the Goy Had placed the food on the fire. Reply

You mention covering the knobs of the oven and compare that to covering the coals. I don't see how this is a valid comparison. When you cover the coals with earth you don't see its effect when Shabbos comes in (as the Alter Rebbe writes at the beginning of Shulchan Aruch HaRav 253 " דַּי בִּקְטִימָה כָּל שֶׁהוּאכד וַאֲפִלּוּ הֻבְעֲרוּ הַגֶּחָלִים אַחַר כָּךְ מֵאֲלֵיהֶם אֵין בְּכָךְ כְּלוּם " So even of no evidence remains that a Kituma was done it is still okay. In our case the Kituma we do is placing the Blech. Reply