Preheat the oven to 350°F. Peel, halve and pit 4 large freestone peaches.
Place the peaches in a baking dish large enough to hold them in one layer. Mix together 1/2 cup orange juice and ¼ cup powdered sugar to dissolve the sugar and then sprinkle over the peaches. Toss gently with your hands until the peaches are evenly coated. Turn the peaches cut side up in the dish.
In a food processor, pulse 1/3 cup slivered almonds, toasted, 1/4 cup packed dark brown sugar, finely grated zest of 1/2 orange until the almonds are in very fine pieces. Add 1 tablespoon cold butter, cut into pieces, and pulse until the mixture is crumbly.
Divide the almond mixture evenly among the hallows of the peaches. Bake until the pan juices are bubbling, 15 to 20 minutes. Serve warm with vanilla ice cream