Whisk together egg yolk, milk, and vanilla; set aside. Pulse flour, confectioner’s sugar, salt, and cardamom in a food processor to combine, about 5 pulses. Sprinkle butter over flour mixture and pulse until mixture resembles coarse crumbs, about 20 pulses. With processor running, add yolk and milk mixture and process until dough comes together, 15–20 seconds. Press dough into the bottom and up the sides of a 4x13-inch tart pan with removable bottom. Cover with plastic and refrigerate at least 1 hour or up to 2 days.

Process hazelnuts in a food processor until coarsely ground, about 15 seconds. Add sugar and process 20 seconds. Add egg, egg white, butter, vanilla and salt and process until smooth, about 30 seconds. Transfer to a bowl and chill until ready to use.

Adjust oven rack to the lower-middle position and heat oven to 375℉. Meanwhile, transfer chilled tart shell to freezer until oven is ready (about 30 minutes). Set frozen tart shell on a baking sheet. Lightly spray a large piece of foil with nonstick spray. Fit foil pieces, greased side down, tightly against frozen tart shell, letting excess hang over sides. Fill foil-lined tart shell with dried beans or pie weights and bake until crust is set and just starting to brown, 25 minutes. Remove foil and weights and bake crust until dry and golden brown, another 5–8 minutes.

Spread hazelnut filling evenly over tart shell and bake until set, about 20 minutes, shielding crust edges if starting to brown too much.

Remove tart from oven and sprinkle 2 tablespoons blue cheese evenly over filling. Gently toss pears with 2 tablespoons lemon juice then arrange pear slices on top of cheese and filling, slightly overlapping. Bake tart until pears are fork-tender, about 25 minutes.

Combine apricot jam and remaining 1 teaspoon lemon juice, microwave for 20 seconds on high; whisk to combine.

Remove tart from oven and brush pears with glaze, sprinkle with additional cheese and hazelnuts. Cool completely in pan before unmolding and cutting.