וּמִסַּ֨ל הַמַּצּ֜וֹת אֲשֶׁ֣ר ׀ לִפְנֵ֣י יְהוָ֗ה לָ֠קַח חַלַּ֨ת מַצָּ֤ה אַחַת֙ וְֽחַלַּ֨ת לֶ֥חֶם שֶׁ֛מֶן אַחַ֖ת וְרָקִ֣יק אֶחָ֑ד וַיָּ֙שֶׂם֙ עַל־הַ֣חֲלָבִ֔ים וְעַ֖ל שׁ֥וֹק הַיָּמִֽין׃
他又從永恆者面前那籃無酵餅中，取出一個無酵餅、一個用油調和的餅和一個薄餅，放在那些脂肪上和右腿上。
Rashi
וחלת לחם שמן AND A CAKE OF OILED BREAD — This was a scalded cake, and it is called “oiled bread” because he used a large quantity of oil for it, equal to that which he used for the cakes and wafers together. So is it explained in Treatise Menachot 78a (also Menachot 89a).
Ibn Ezra
one maṣṣa cake this is the “one loaf of bread” [Exodus 29:23]. “Loaf” [Hebrew: kikkar] is probably a unit of weight, but not the kikkar used to weigh gold and silver.
Siftei Chakhamim
Use much oil. Rashi is answering the question: Why is it not written חלת מצה שמן in the earlier part of the verse [and שמן would then refer to everything mentioned in the verse], or at the end: ורקיק שמן, and would then refer to everything mentioned beforehand? He explains: [That is the scalded dough, in which he would use much oil].