Preheat the oven to 350 F degrees.Put butter into the bowl, add sugar, flour, salt and buttermilk. Make sure that the ingredients are cold and kneed a nice dough gently. Put it in the plastic bag and leave it to rest a few minutes.Cook the cherries with sugar on the medium heat. Put the cornstarch in the cup and mix with some water. Stir the cornstarch in cherries to make a jelly. Take of the heat and sprinkle in the semolina. Leave it to cool.Mix the cold butter pieces with rolled oats, flour, brown sugar and salt. Make crumbs with your hands.Make a dough shell in the 9 inch pie pan. Pour the cold cherry filling and sprinkle the dough crumbs on the top. Bake for 65 minutes or until light brown.
Notes
The pie should be cooled completely at room temperature before slicing.