Rinse the nectarines, cut in half and pit. Cut the halves into wedges. Preheat the oven to 180°C (approximately 350°F).
Whisk the eggs, sugar, cinnamon and lemon zest until fluffy. Sift the flour, salt and baking soda together then fold into the egg mixture, alternately with the milk.
Grease the tart pan with butter and sprinkle with ground almonds. Arrange the nectarines in the pan, pour the batter over top and bake in a preheated oven (160°C) (approximately 325°F) for 50 minutes.
Remove the clafoutis and let cool slightly. Dust with powdered sugar and serve with vanilla ice cream, if desired.