In a small skillet, melt 1 tablespoon butter over medium heat. Add nectarines and cook about 4 to 5 minutes, until softened. Remove from heat.
Spread each slice of bread with cream cheese. Divide nectarines evenly among four slices of bread and top with remaining bread to build sandwiches.
In a shallow dish, whisk eggs, milk, sugar, and vanilla. Carefully dip sandwiches into egg mixture and turn to coat.
Melt remaining butter on a griddle over medium heat. Cook sandwiches about 2 to 3 minutes per side, or until golden brown. Dust with confectioners' sugar and serve.