This refers to Yahweh's presence, meaning that Yahweh saw everything that happened. Alternate translation: "in Yahweh's presence" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Here the word "fire" is used to refer to "burning incense." Alternate translation: "they burned an incense offering in a way that Yahweh did not approve of" (See: [[rc://en/ta/man/translate/figs-metonymy]])