You will need frozen rabbit at least twice in Dragon Ball Z Kakarot, once for the main story, and once for a sub story. But finding it is not necessarily very intuitive. Forget the supermarket and the butcher, why make it simple when you can make it complicated?
DBZ Kakarot: Frozen rabbit
Head to Darlinge Ice Lake, in the Northern Mountain Zone, look for large blocks of ice around the lake, then break them up with a ball of energy. This will automatically release the frozen rabbit meat. There are several blocks in the area, so feel free to go around. You can see the position of 3 of them on the map above, but there are more. If necessary, you can leave the area and then go back if you don't get enough meat. Saving and loading also works.
Rewards
To improve the DBZ Kakarot training room, you will need special components and materials such as purple meteorite, red meteorite, and those of other colors. Here are their location and how to get them.
