You can simply compare the rates. Platforms like Fidelity let you compare across the board. For direct bank CDs, sites like depositaccounts.com do a good job of showing current rates.
Right now in general Treasury Bills are offering the highest rates for up to 6 months (26 weeks) offering 5.3-5.5%, and pretty competitive at 52 weeks as well.
For 12, 18 and 24 months CDs appear to be offering the best rates 5.3-5.4%. Brokered CDs specifically although some direct bank CDs may be competitive. You do have to watch out for call protection on the longer brokered CDs. At 12 months or higher this can reduce the rates a bit.
I’m only talking about no credit risk fixed income here.