Yes, a general officer not only can but is typically required to be the convening authority for a general court-martial involving a field grade officer (a Major, Lieutenant Colonel, or Colonel). The authority to convene a general court-martial—the military’s highest level of trial court—is limited by the UCMJ to very senior commanders, almost always general or flag officers.
The rules for courts-martial specify that the convening authority must be a commander who has the authority to convene a general court-martial and who is not an “accuser” in the case. For a case involving a field grade officer, the convening authority will be a general officer who is superior in the chain of command to the accused officer. This could be a division commander, a corps commander, or another senior general officer designated with this authority. This ensures that a serious case involving a senior officer is handled at an appropriately high level.
A military defense attorney will always verify that the convening authority has the proper jurisdiction and authority over their client. If a commander who lacks the proper authority attempts to convene a court-martial, the entire proceeding is jurisdictionally flawed. For a field grade officer, this means ensuring that the commander who referred the charges to trial is, in fact, a general officer who has been properly empowered to convene general courts-martial.