For the almond pasta frolla, combine the dry ingredients in a bowl and mix well. Rub in the butter until it is absorbed, making sure the mixture remains cool and powdery and does not become pasty. Beat the egg and stir in with a fork. Continue stirring until the dough holds together, then knead it briefly, just until smooth. Shape into a disk, wrap in plastic, and refrigerate at least 1 hour, or until firm.
Rinse and hull the strawberries. Choose the best and most symmetrical ones to form the border of the tart. (Draw a 9-inch circle on a piece of parchment or wax paper and arrange the berries inside the line to see how many you will need.) Slice the remaining berries into a bowl and add the sugar and lemon juice. Toss to combine and cover with plastic wrap. Refrigerate the sliced and whole berries until ready to assemble the crostata.
To form the tart base, roll out three-fourths of the dough on a floured surface into a 9-inch disk. Transfer to a cookie sheet lined with parchment or buttered wax paper. Place a 9-inch disk, like a springform bottom or plate, on the dough and trim it to a perfect 9-inch-diameter circle. Pierce the dough all over with a fork at ½-inch intervals. Combine the scraps with the remaining dough and roll into a thin cylinder, about 30 inches long. Moisten the edge of the base with water and arrange the cylinder of dough on top of it to form the sides of the tart shell. Press the cylinder with your fingertips to make it adhere and mark a series of diagonal lines on it with the back of a small knife, as in the illustration. Bake at 350 degrees for about 25 minutes, until the dough is an even golden color and feels firm when pressed with a fingertip. Cool the tart shell on a rack on the cookie sheet.
To assemble the crostata, place the cooled shell on a platter. Spread the bottom evenly with the jam. Arrange a row of the reserved whole strawberries inside the edge. If the berries are very large, halve them. Drain the sliced berries well and pile them in the center. Dust with the confectioners’ sugar before serving.