Another interpretation. Rav Asi said in the name of Rabbi Yochanan: An oven that one heated and then swept out [of its coals] and roasted the Pesach inside it, this is not "roasted by fire," because it is stated "roasted by fire, roasted by fire" two times [requiring direct fire]. Our Rabbis taught: If one cut it up and placed it upon coals, Rabbi says: I say this is "roasted by fire." But did Rabbi say a coal is called fire? They raised a contradiction: "a burn from fire" (Leviticus 13:24); from this I know only one who was burned by fire. By a coal, by hot ash, by boiling lime, by boiling plaster, and by anything that comes by means of the flame, to include water heated by fire, from where do we learn these? The verse teaches "a burn, a burn," the repetition includes them. The reason is that the Merciful One said "a burn, a burn"; but were it not so, I would have said a coal is not called fire. Ravina said: combine and teach it as "a burn from fire." From this I know only one burned by fire and by a coal; one burned by hot ash, by boiling lime, and so forth.
Coals and a Swept Oven and What Counts as Fire
Yalkut Shimoni on Torah 198:3
דָּבָר אַחֵר. אָמַר רַב אַסִּי אָמַר רַבִּי יוֹחָנָן, תַּנּוּר שֶׁהִסִּיקוֹ וּגְרָפוֹ וְצָלָה בּוֹ אֶת הַפֶּסַח אֵין זֶה צְלִי אֵשׁ, מִשּׁוּם שֶׁנֶּאֱמַר צְלִי אֵשׁ צְלִי אֵשׁ שְׁנֵי פְּעָמִים. תָּנוּ רַבָּנָן, חֲתָכוֹ וּנְתָנוֹ עַל גַּבֵּי גֶּחָלִים, רַבִּי אוֹמֵר, אוֹמֵר אֲנִי זֶה צְלִי אֵשׁ. וּמִי אָמַר רַבִּי גַּחֶלֶת אִיקְרִי אֵשׁ, וְרַמִּינְהוּ (ויקרא יג, כד) "מִכְוַת אֵשׁ" אֵין לִי אֶלָּא שֶׁנִּכְוָה בְּאֵשׁ, בְּגַחֶלֶת, בְּרֶמֶץ בְּסִיד רוֹתֵחַ, בְּגַפְסִיס רוֹתֵחַ וּבְכָל דָּבָר הַבָּא מֵחֲמַת הָאוּר לְרַבּוֹת חַמֵּי הָאוּר מִנַּיִן תַּלְמוּד לוֹמַר מִכְוָה מִכְוָה רִבָּה. טַעְמָא דְּאָמַר רַחֲמָנָא מִכְוָה מִכְוָה הָא לַאו הָכִי הֲוָה אֲמִינָא גַּחֶלֶת לֹא אִיקְרֵי אֵשׁ. אָמַר רַבִינָא כְּרִיךְ וְתַנִי מִכְוַת אֵשׁ. אֵין לִי אֶלָּא שֶׁנִּכְוָה בְּאֵשׁ וְגַחֶלֶת, נִכְוָה בְּרֶמֶץ בְּסִיד רוֹתֵחַ וְכוּ'.