Not in my computer, but it could be something like this:
FVector direction = TargetLocation- GetActorLocation();
direction.Normalize();
auto lookat = FRotationMatrix::MakeFromX(direction).Rotator();
lookat.Pitch = 0.0f;
lookat.Roll = 0.0f;
SetActorRotation(lookat);
Where TargetLocation is as the name suggests, the location of the actor you want to look at. I set Pitch and Roll to zero, because I only wanted to turn