UWP XAML NavigationView - CornerRadius on Content Panel

I am new to XAML and I am implementing a NavigationView control in my UWP application.

Some details:

• Visual Studio 2019
• Microsoft.UI.Xaml version 2.6.2 (Nuget Package Installed)

UWP Targets:

• Target: Universal Windows

• Target Version: Windows 10, version 2004 (10.0; Build 19041)

• Min Version: Windows 10 Fall Creators Update (10.0; Build 16299)

I am trying to find the property or style that controls the top left corner radius of the "content" section. I would like to not have a rounded corner there, and just to flow directly to the top but I can't seem to find the correct way to do this. Attached is a picture of the rounded corner I am talking about: content frame.

Here is the XAML for my main page with the navigation menu:

<Page
x:Class="NavTest.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:muxc="using:Microsoft.UI.Xaml.Controls"    
xmlns:local="using:NavTest"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<Grid>
    <muxc:NavigationView x:Name="NavView" Background="Gray">
        <muxc:NavigationView.MenuItems>
            <muxc:NavigationViewItem Tag="home" Icon="Home" Content="Home"/>
            <muxc:NavigationViewItemSeparator/>
            <muxc:NavigationViewItemHeader x:Name="MainPagesHeader"
                                       Content="Main pages"/>
            <muxc:NavigationViewItem Tag="apps" Content="Apps">
                <muxc:NavigationViewItem.Icon>
                    <FontIcon FontFamily="Segoe MDL2 Assets" Glyph="&#xEB3C;"/>
                </muxc:NavigationViewItem.Icon>
            </muxc:NavigationViewItem>
            <muxc:NavigationViewItem Tag="games" Content="Games">
                <muxc:NavigationViewItem.Icon>
                    <FontIcon FontFamily="Segoe MDL2 Assets" Glyph="&#xE7FC;"/>
                </muxc:NavigationViewItem.Icon>
            </muxc:NavigationViewItem>
            <muxc:NavigationViewItem Tag="music" Icon="Audio" Content="Music"/>
        </muxc:NavigationView.MenuItems>
    </muxc:NavigationView>
</Grid>

Does anyone know how I can control the top left corner radius of the navigation menu content item to make it not rounded? Is there a style property I can override or set? Just directly setting the "CornerRadius" property on the NavigationView doesn't seem to make any difference.

Thanks