1. Place oven rack in the lower third of oven. Preheat oven to 375°.
2. Place 2 tablespoons hazelnuts in a small bowl; set aside. Place remaining hazelnuts and sugar in a food processor; process until finely ground. Add butter, salt, and egg; process until a smooth paste forms.
3. Gently roll pie dough into a 16 x 12-inch rectangle, cutting dough and gently pinching seams as needed to create shape. Fit dough into a 14 x 4 1/2-inch removable-bottom metal tart pan lightly coated with baking spray. Gently press dough against bottom and sides of pan. Spread hazelnut mixture evenly over bottom of dough. Bake in lower third of oven at 375° for 20 minutes or until lightly browned. Remove from oven. Sprinkle blue cheese evenly over top.
4. Gently toss pears with lemon juice. Arrange pear slices on top of cheese. Bake at 375° for 25 minutes or until pears are tender when pierced with the tip of a knife. Remove from oven. Place jelly and 1 teaspoon water in a small microwave-safe bowl; microwave at HIGH 1 minute or until mixture boils. Brush top of tart with jelly mixture; sprinkle with remaining 2 tablespoons hazelnuts. Cool completely in pan on a wire rack before slicing.