What is the best way to power a 90v DC motor?
You need enough batteries connected in series to add up to 90 volts plus an electronic speed control (ESC) unit. Without the ESC, the motor will draw a lot more than 22 amps for a short time every time you switch it on. It will try to accelerate to full speed as fast as it can. That will be hard on both the motor and the battery and could destroy both very quickly. The ESC will limit the current and control the acceleration.

You could use a lower battery voltage and a boost DC to DC converter, but then the battery current will be higher than the motor current. You may or may not be able to find such a thing.

90-volt motors are usually intended to work with an ESC that takes a 120 volt AC input. Some such controllers may accept either AC or DC input. A 90-volt ESC rated for DC input may be difficult to find. You might be better off looking for a lower voltage motor.