Heat oven to 375ºF with rack in the lower third. In a food processor, combine almond paste, 1 egg, cornstarch and salt until completely blended.
Roll crust on flour-dusted parchment into a 12- to 13-inch circle. Spread almond mixture in the center, leaving a 2-inch space around the edge.
Toss pears with lemon juice and arrange on top of almond mixture. Gently fold over crust edge, pleating, just covering edges of pears. Transfer crostata, on parchment, to a baking sheet. Whisk remaining egg and brush edge of crust with a little egg wash.
Bake until crust is deep golden and pears are soft, about 40 min; cover crostata loosely with foil for the last 10 min to prevent overbrowning. Heat apricot preserves and brush over pears. Sprinkle with almonds and serve warm or cooled.
Here I've used Bosc pears for my filling. They have a brown skin and when baked, hold their texture quite well. For this crostata I want a pretty pear arrangement, so a darker skinned pear is nice. Red Anjou or even a Red Bartlett would be lovely as well. If you have green Anjou or the more yellow Bartlett pears, they will work just deliciously. You just won't get the defined design. It will still be beautiful.