diff --git a/eng/SourceBuild.Tarball.targets b/eng/SourceBuild.Tarball.targets
index 3948a9cc6e..604d96e571 100644
--- a/eng/SourceBuild.Tarball.targets
+++ b/eng/SourceBuild.Tarball.targets
@@ -1,11 +1,15 @@
 <Project>
 
+  <UsingTask AssemblyFile="$(XPlatSourceBuildTasksAssembly)" TaskName="AddSourceToNuGetConfig" />
+  <UsingTask AssemblyFile="$(XPlatSourceBuildTasksAssembly)" TaskName="RemoveInternetSourcesFromNuGetConfig" />
+
   <Target Name="PackSourceBuildTarball"
           Condition="'$(PackSourceBuildTarball)' == 'true'"
           DependsOnTargets="
             GetTarballDirProps;
             AddTarballSource;
             AddTarballSourcelinkMetadata;
+            GenerateTarballSmokeTestNuGetConfig;
             AddTarballTools;
             AddTarballPackages;
             AddTarballExternalTarballs;
@@ -106,6 +110,23 @@
       DestinationFiles="@(ArtifactsGitDir -> '$(TarballSourceDir)%(RecursiveDir)%(Filename)%(Extension)')" />
   </Target>
 
+  <Target Name="GenerateTarballSmokeTestNuGetConfig">
+
+    <Copy
+      SourceFiles="$(ProjectDir)smoke-testNuGet.Config"
+      DestinationFiles="$(ProjectDir)artifacts\tarball-smoke-testNuGet.Config" />
+
+    <RemoveInternetSourcesFromNuGetConfig
+      NuGetConfigFile="$(ProjectDir)artifacts\tarball-smoke-testNuGet.Config"
+      OfflineBuild="false"
+      RemoveFeedPrefixes="darc-pub-dotnet-" />
+
+    <AddSourceToNuGetConfig NuGetConfigFile="$(ProjectDir)artifacts\tarball-smoke-testNuGet.Config"
+                            SourceName="smoke-test feed"
+                            SourcePath="SMOKE_TEST_PACKAGE_FEED" />
+
+  </Target>
+
   <Target Name="AddTarballTools">
     <ItemGroup>
       <TarballRootToolFile
@@ -166,13 +187,13 @@
         in it to generate a full set of smoke-test-prereqs. This isn't necessary in the tarball
         because we have those smoke-test-prereqs, but we hit authentication errors nonetheless. Copy
         a trimmed down nuget.config in this case.
-        TODO: Automatically trim down the main nuget.config.
       -->
       <TarballCopyFile
-        Condition="Exists('$(ProjectDir)support\tarball\smoke-testNuGet.Config')"
-        Include="$(ProjectDir)support\tarball\smoke-testNuGet.Config"
+        Condition="Exists('$(ProjectDir)artifacts\tarball-smoke-testNuGet.Config')"
+        Include="$(ProjectDir)artifacts\tarball-smoke-testNuGet.Config"
         RelativeDestination="smoke-testNuGet.Config" />
 
+
       <!-- Setup package version props to include both source-built and running PackageVersions.props -->
       <TarballCopyFile
         Include="$(ProjectDir)support\tarball\PackageVersions.props"
diff --git a/support/tarball/smoke-testNuGet.Config b/support/tarball/smoke-testNuGet.Config
deleted file mode 100644
index d17b96948d..0000000000
--- a/support/tarball/smoke-testNuGet.Config
+++ /dev/null
@@ -1,10 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-  <packageSources>
-    <!--To inherit the global NuGet package sources remove the <clear/> line below -->
-    <clear />
-    <add key="source-built-packages" value="SOURCE_BUILT_PACKAGES" />
-    <add key="dotnet-core" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-public%40Local/nuget/v3/index.json" />
-    <add key="smoke-test feed" value="SMOKE_TEST_PACKAGE_FEED" />
-  </packageSources>
-</configuration>
diff --git a/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks.XPlat/RemoveInternetSourcesFromNuGetConfig.cs b/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks.XPlat/RemoveInternetSourcesFromNuGetConfig.cs
index 65aa69ac80..05036ed2ed 100755
--- a/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks.XPlat/RemoveInternetSourcesFromNuGetConfig.cs
+++ b/tools-local/tasks/Microsoft.DotNet.SourceBuild.Tasks.XPlat/RemoveInternetSourcesFromNuGetConfig.cs
@@ -34,6 +34,13 @@ public class RemoveInternetSourcesFromNuGetConfig : Task
         /// </summary>
         public string[] KeepFeedPrefixes { get; set; }
 
+        /// <summary>
+        /// A list of prefix strings that make the task remove a package source unconditionally. For
+        /// example, a source named 'darc-pub-dotnet-aspnetcore-e81033e' will be removed if the prefix
+        /// 'darc-pub-dotnet-aspnetcore-' is in this list.
+        /// </summary>
+        public string[] RemoveFeedPrefixes { get; set; }
+
         public override bool Execute()
         {
             XDocument d = XDocument.Load(NuGetConfigFile);
@@ -52,6 +59,13 @@ public override bool Execute()
                         return true;
                     }
 
+                    if (RemoveFeedPrefixes
+                        ?.Any(prefix => feedName.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
+                        == true)
+                    {
+                        return false;
+                    }
+
                     string feedUrl = e.Attribute("value").Value;
                     if (OfflineBuild)
                     {