Place the flour, hazelnuts (or almonds) and baking powder in a bowl. Put the unsalted butter and sugar in a food processor. Pulsate the ingredients until they are fluffy and add the egg. Add the dry ingredients and mix until it looks like cornmeal. Add 1/2 of the water and process for 30 seconds. Feel the dough; it should stick together, if it doesnât add the remaining water. Place the dough wrapped in plastic wrap in the refrigerator while you are preparing the filling.
Rub about 1 tablespoon of butter onto a spring form pan. Press 2/3 of the dough on the bottom and up the sides to about 1â of the top of the pan. The remaining dough will be crumbled over the top.
Put all the filling ingredients in a bowl and coat the cherries well. Taste for sweetness. The type of cookies that you use will determine if additional sugar is needed. Spread the filling in the prepared crust. Crumble the remaining dough over the top of the cherry mixture.
Place the tart into the middle of the oven and bake at 350ÂºF for 1 hour.
Release the spring form the pan and allow the tart to cool. Serve the tart warm or room temperature with a spoon full of crÃ¨me fresh over the top.