Make the pastry: place the flour in a bowl of a food processor. Add the egg yolk, sugar, ground pecans, and salt. Pulse a couple of times to mix. Add the butter and pulse until butter is pea-sized. Add two tablespoons of ice water and pulse, adding more water, a tablespoon at a time, only until dough starts to come together in bowl. Turn out onto floured board, knead lightly into a ball, cover with plastic wrap and refrigerate for at least one hour.
Preheat oven to 350°F.
Roll out the dough to 1/8” thickness. Drape over 8” tart pan with fluted removable sides. Trim dough 1” larger than the sides of the pan and tuck excess dough under the edge.
Place a piece of aluminum foil over dough and place pie weights or dry beans over foil. Bake for 25 minutes. Remove weights and foil and continue baking, another 15-20 minutes, or until tart is golden brown. Remove from oven and remove foil and weights. Cool tart crust.
Meanwhile, in medium bowl, combine dulce de leche and pecans. Spread mixture in tart crust. Top with coconut. Serve with berries if desired.