While the oven is preheating, prepare your nectarines. Slice the nectarines in half, scooping out the pit (like an avocado).
Using a fork, make several punctures in each half to allow the bourbon to soak in.
Place all four halves in a baking dish, cut side up. Combine bourbon and vanilla together in a measuring cup and pour into the cavities of the nectarines allowing the liquid to pool where the pit was. If there is any excess pour around the nectarines in the baking dish.
Bake in preheated oven for 20 minutes.
While the fruit is in the oven, combine the sugar and cardamom to sprinkle on top.
When the nectarines are finished in the oven, sprinkle the tops generously with the cardamom sugar.
Using a culinary torch, brulee the sugar on top of the nectarines until golden brown and hard. Alternatively, you can turn your oven up to broil and stick them under the broiler for a couple minutes. Just make sure you do NOT take your eyes off of them.
Serve warm with a scoop (or two) of vanilla ice cream and a spoonful of any leftover warm bourbon.