Chef Lidia Matticchio Bastianich
If the ice cream is frozen solid, let it stand at room temperature while preparing the tomatoes.
With a vegetable peeler, remove the zest (orange part of the peel only, not the underlying white pith) from the orange in wide strips.
Cut the zest into very thin strips.
Squeeze the juice from the orange and reserve the strips of zest and juice separately.
In a medium-size, heavy, nonreactive skillet or saucepan, make a caramel with the sugar and water.
Place over medium heat and cook, stirring occasionally, until the sugar is melted and the syrup is boiling.
Don't stir the syrup after it comes to a boil, as this will most likely form crystals in the syrup.
Cook, swirling the pan occasionally to prevent the syrup from hardening on the sides of the pan, until the syrup begins to turn a very pale golden brown.
Reduce the heat to low and continue cooking and swirling until the syrup is medium amber color (340 degrees on a candy thermometer).
If the caramel begins to color too quickly, dip the bottom of the skillet or saucepan in a basin of cool water for a second or two.
Carefully add the orange zest and orange juice to the medium amber-colored caramel.
Return the pan to the heat and bring to a boil, stirring constantly to dissolve any caramel that has hardened.
Add the tomatoes and Grand Marnier.
Let the sauce boil until thickened, about 2 minutes.
Scoop the ice cream into shallow dishes and spoon some of the tomatoes and the hot syrup over each serving.
Garnish with mint sprigs.