Raspberry Jam:  Make the jam at least one day (or up to 10 days) before making the Crostata. In a small bowl stir the pectin into the sugar. Place the frozen unsweetened raspberries and the sugar mixture in a medium sized saucepan and, over medium heat, bring to a boil, stirring frequently. When it's at a full boil, adjust the heat to keep the mixture at a full boil and, stirring frequently, cook for about six minutes. Do not let it burn. (As the jam boils, you will notice large bubbles and some foam. You can skim off the foam if you like. As the jam continues to boil the foam will subside, the bubbles will get smaller, and the jam will become darker in color, with a glossy sheen.) Remove from heat and, if you like, do the Freezer Test to check its consistency. To do this, place a little jam on a frozen spoon, wait a minute for the jam to cool down, and check the consistency. If the jam isn't firm enough, return the saucepan to the heat and cook a little longer. Once made, stir in the lemon juice and strain if you want to remove the seeds. Transfer to a heatproof jar or bowl and let cool. Then cover and store in the refrigerator. You will need 3/4 cup (225 grams) of raspberry jam for this crostata. This recipe makes about 1 1/2 cups (450 grams) of raspberry jam.

Pastry: In your food processor, place the flour, salt, and sugar and process until combined. Add the cold butter and process (using the pulse button), until the mixture is crumbly (resembles coarse meal). Pour the ice water, one tablespoon at a time, through the feed tube, and process (pulse) just until the dough is moistened and starts to clump together when pinched (it should not be a solid ball of dough). Turn the dough out onto your counter and gather into a ball. Flatten into a disk, cover with plastic wrap, and refrigerate for about 30 - 60 minutes, or until firm enough to roll out. (The pastry can be refrigerated for a few days or frozen for a month. If frozen, defrost in the refrigerator overnight before using.)

Preheat your oven to 400 degrees F (200 degrees C). Line a baking sheet with parchment paper (or butter your baking sheet).

Once the pastry has chilled, remove from refrigerator and place on a lightly floured surface. Roll the pastry into an 11 inch (28 cm) round. To prevent the pastry from sticking to the counter and to ensure uniform thickness, keep lifting up and turning the pastry a quarter turn as you roll (always roll from the center of the pastry outwards to get uniform thickness). Transfer the pastry to your baking sheet. Spread the raspberry jam onto the pastry, leaving a 2 inch (5 cm) border. Gently fold the edges of the pastry up and over the filling, pleating as necessary. Make sure to seal any cracks in the pastry.

Bake for about 35 minutes or until the pastry is golden brown. Remove from oven and place on a wire rack to cool.  Sprinkle with chopped nuts, if desired. Serve plain or with softly whipped cream or vanilla ice cream.

Makes about 6 - 8 servings.