Customizing Listview Groupheader

Hi All!!

Hope everyone is doing well.

I am trying to customize the GroupHeader of a listview. I would like it to stretch under the jumplist (like default behavior - see left image).

This is the xaml I am using.

<ListView.GroupHeaderTemplate>
  <DataTemplate>
    <ViewCell Height="50">
      <StackLayout VerticalOptions="FillAndExpand"
                   Padding="5"
                   BackgroundColor="#3498DB">
        <Label Text="{Binding Key}" TextColor="Black" VerticalOptions="Center"/>
      </StackLayout>
    </ViewCell>
  </DataTemplate>
</ListView.GroupHeaderTemplate>

How can I get the custom groupheader to stretch so that it is scroll under the jumplist?

Thanks
Noel