You have two options here.
For maximum accuracy, the way to go would be to put a 50A CT around each of the red and black wires. Those wires are carrying up to 50A each, so you don’t want to pass both of them through one 50A CT.
Or, if you’re okay with a little inaccuracy and would rather use one of those two CTs for something else, you could put one 50A CT around either the red or black wire, then double it. The reason this mostly works out is that all the major loads in a range, the heating elements, will be running on 240V, so this measurement method will be perfectly accurate for them. The 120V loads are usually only the oven light and maybe some control circuitry, which is almost negligible compared to the large draw of the heating elements, and so won’t affect things too much.