Sanes

Route::controller(PostController::class)->prefix('blog')->name('blog.')->group(function (){
    ...
    Route::get('{id}-{alias}', 'show')->name('show');
    ...
});

public function show($id, $alias)
    {
        $post = Post::with('comments')->where(['id' => $id, 'alias' => $alias])->firstOrFail();
        return view(config('cms.theme').'.posts.show', ['post' => $post]);
    }