What was Tai cooking in the Digimon movie? In the first movie we can see Tai cooking something yellowish. Does someone knows what kind of food was he making?
You might actually be referring to the omuraisu (rice omelette) that Tai cooked for himself, his sister Kari, and Koromon in Digimon Adventure Episode 21, around the 8:38 mark. It's possible that you mistook that scene for being a part of the second part of Digimon: The Movie due to the fact that it takes place in the real world and has a similar washed-out color scheme.

Here's an album of relevant screenshots from that episode.

However, if you're actually referring to Digimon: The Movie, like Eric stated above in the comments, Tai cooks an egg in the first part of the movie, around the 7:33 mark. I don't believe there are any other scenes of him cooking anything else for the rest of Digimon: The Movie.

Here's an album of relevant screenshots from the movie.