It is called Momotaro Gold and apparently, based on earlier discussions here about it, seeds are only available from Japanese growers as it is supposedly an unstableF2 hybrid of the regular F1 pink. Some are gold, some are red, and some are stripped.

Save your seeds from any yellow ones, grow it out next year and see if you can get it to stabilize.

Dave

I grew a plant this year and it produced large beefsteak sized fruit, but I won’t do it again. This is the most bland tomato I’ve ever grown. If you like zero acid this might be for you. Also they have a tendency to go mealy.