Toss nectarines, 2 cups raspberries, and 1/4 cup sugar in medium bowl. Let stand until juices form, about 5 minutes.
Whisk egg yolks, nectar, liqueur, salt, and 1/4 cup sugar in large metal bowl to blend. Place bowl over saucepan of boiling water; whisk until mixture is thick and thermometer inserted into center registers at least 160°F, about 6 minutes.
Divide fruit mixture among 4 large glasses. Spoon warm peach sabayon over. Garnish with remaining berries and sliced almonds, if desired.
