Using filament form layout store belongsTo many relation data

Question

I have 2 models User and Restaurant.

Where the user has many restaurant relations concepts.

Models\User.php

public function restaurants(): HasMany
{
    return $this->hasMany(Restaurant::class);
}

Models\Restaurant.php

// Columns
// 'user_id', 'name',

public function user(): BelongsTo
{
    return $this->belongsTo(User::class);
}

Now, I have a form in the RestaurantResource where I have used

Forms\Components\Fieldset::make('Owner Details')
    ->relationship('user')
    ->schema([
      // Inputs
    ]),
    
Forms\Components\Fieldset::make('Restaurant Details')
    ->schema([
        // Inputs
    ])

but I am getting this error.

I have also reviewed the official documentation https://filamentphp.com/docs/3.x/forms/advanced#saving-data-to-relationships but I feel I have followed the correct steps.