Preheat oven to 375*In a bowl cream butter and sugar well. Add egg and mix until well blended. Add salt and flour and mix with a rubber spatula or spoon. When it all comes together into a dough ball press into the tart pan and trim off the excess.Fill the crust with the chopped nuts and spread it out to make an even layer. Pour the condensed milk over and carefully spread it all over the nuts.Put tart pan on a baking sheer and put into the oven. Bake for 25-35 min or until golden brown all over. You may see several dark spots but that's ok.Cool completely slice and serve.