Preheat over to 325 F. Grease and flour Bundt cake pan and tunnel.
In the bowl of a stand mixer, beat together sugar and butter. Add eggs, one at a time, mixing well after each.
In a medium mixing bowl, sift together flour, baking powder and salt. Alternately add the flour mixture and the milk to the sugar and butter, beating well after each addition. Blend in vanilla and rose syrup. Pour batter into prepared pan. Let rest 10 minutes.
Place tunnel pan on top of filled Bundt pan. Bake 60 minutes or until cake tester comes out clean. Cool 10 minutes.
Remove from pan and cool completely on cooling rack. When cake is cool, place it bake in Bundt pan and refrigerate 8 hours or overnight.
Just before serving, remove cake from refrigerator. While still in pan, fill tunnel with sorbet. Invert filled cake onto serving platter.
To make glaze
In a small mixing bowl, whisk together sugar, syrup, butter and lemon juice. Just before serving, pour glaze over cake.