How to access an array property from a class wrapped inside observable in angular?

I am trying to populate a dropdown by accessing an array property from the class which is wrapped inside an observable.

I have an interface like below :

export interface IApplicationConfigurationResponse
{
   settings?: Settings[] ] undefined;
}

export class ApplicationConfigurationResponse
{
   settings?: Settings[] ] undefined;
}

export class Settings 
{
   settingId!:number;
   name!:string;
}

state-management.service.ts:

@Injectable
export class StateManagementService
{
    private subjectConfigurations =  new BehaviourSubject<ApplicationConfigurationResponse>(null);
    
    getApplicationConfigurations(){
       return this.subjectSettings.asObservable().pipe(filter(k) => k!=null);
    }
    
    set saveApplicationConfiguration(state: ApplicationConfigurationResponse)
    {
        this.subjectConfigurations.next(state);
    }
}

master.component.ts:

@Component({
selector: 'app-master',
..
..
})

export class MasterComponent implements OnInit
{
    constructor(private myService: MyService,
                private stateService: StateManagementService) {}
                
                
    ngOnInit():void {
    this.myService.getApplicationConfigurationsFromBackend().subscribe((res) ==> {
       this.stateService.saveApplicationConfiguration = res;
    }
}

header.component.ts:

@Component({
selector: 'app-header',
..
..
})

export class HeaderComponent implements OnInit
{
    applicationConfigurationResponse$ : Observable<ApplicationConfigurationResponse>();
    constructor(private stateService: StateManagementService) {}
                        
    ngOnInit():void {
       this.applicationConfigurationResponse$ = this.stateService.getApplicationConfigurations;
    }
}

header.component.html:

<div>
       <select class="dropdown">
            <option *ngFor="let setting of applicationConfigurationResponse$.settings | async" [value] = "setting.settingId">
                  {{ setting.name }}
             </option>
       </select>  
</div>

But I am getting error on below line:

I am not able to access the property which is wrapped inside an observable.

How can I access the Settings[] from ApplicationConfigurationResponse and populate a dropdown?