IN A MEDIUM-SIZE, NON-REACTIVE saucepan, combine the 1 1/2 cups sugar, the split vanilla bean, lemon zest, lemon juice and 4 cups water. Bring to a boil, reduce to a simmer and cook, stirring, until the sugar is dissolved and the syrup is clear. Peel the pears, cut in half lengthwise, seed, core and stem. Shape 1/2 of 1 pear into a peach-like round by cutting off the stem end. Poach the pear halves in the sugar syrup until tender. Drain on a rack. Preheat oven to 350F. On a baking sheet, toast the almonds to golden brown, cool and pulverize in a food processor. Heat the milk with the remaining 2-inch piece of vanilla bean. Meanwhile, beat the eggs, yolks and 3/4 cup sugar until thick and lemon colored, then add the flour. When the flour is absorbed, add the milk, return to the heat, stirring, and cook 3-5 minutes, or until nicely thickened. Pour pastry cream into a bowl and stir in the 6 tablespoons of butter. Add the almond powder, macaroons, and 1/2 cup kirsch. Allow to cool to room temperature, stirring occasionally; cover with plastic wrap and refrigerate to chill. Heat the apricot jam, then rub through a fine sieve and add the 1/4 cup kirsch. Heat again and stir constantly until clear. Spread a thin layer of apricot glaze on bottom of the baked and cooled pastry shell. Spoon in the frangipane (almond pastry cream) and smooth it out. Set the pear round in the center and arrange around it the pear halves, stem end facing center. Press pears gently into the frangipane. Brush the apricot glaze over the pears; mix the pistachios and sprinkle over the pears. Refrigerate until 15 minutes before serving. (Can be made 1 day in advance.)