Make the dough: In a large bowl, mix together the flour, sugar and salt. Add the butter and start working the butter into the flour with your hands until there are pieces the size of large peas.
Add the water and continue mixing just until the dough comes together. Do not overwork the dough. Cover with plastic wrap, press down to flatten the dough into a disk and refrigerate for at least 30 minutes before rolling out.
Preheat oven to 400ºF/200ºC. Remove dough from fridge.
Working on a lightly floured surface roll out the dough into a 14-inch/35 cm. circle, about ?-inch/½-cm thick. Place dough onto a baking sheet lined with parchment paper.
In a small bowl, mix together the ground almonds and ¼ cup of sugar. Sprinkle half of the mixture over the dough, leaving a 1½-inch/4-cm. border. Arrange the nectarines in concentric circles, making only one snug layer. Sprinkle the remaining almond sugar mixture over the fruit.
Fold the border of dough into the nectarine, pinching the edges to make sure they are sealed. Brush the border with the melted butter and sprinkle it with the remaining 2 tablespoons of sugar.
Bake in the lower section of the oven for 45-50 minutes, until the crust is well browned and its edges are slightly caramelized. Remove from oven and allow to cool for 20 minutes before serving.
Brush the galette with warmed jam, honey or maple syrup and serve with ice cream!