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1
Preheat the oven to 325.
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2
On a parchment paperlined baking sheet, toast the pecans for about 12 minutes, until lightly browned and fragrant.
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3
Let cool.
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4
In a medium skillet, cook the oats over moderate heat, tossing frequently, until fragrant and lightly toasted, about 4 minutes.
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5
Let cool.
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6
In a food processor, pulse the flour with the toasted pecans until the nuts are finely ground.
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7
Transfer to a medium bowl and stir in the oats, light brown sugar, granulated sugar, salt, black pepper and cinnamon.
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8
Using a fork, stir in the butter until large clumps form.
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9
Spread the streusel on the parchment-lined baking sheet in a single layer and bake for about 25 minutes, until golden brown.
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10
Let cool.
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11
Increase the oven temperature to 350.
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12
Generously butter and flour a 10-inch Bundt pan.
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13
In a large bowl, combine 1/4 cup of the sugar with the cornstarch, nutmeg, cinnamon and allspice.
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14
Add the apples and toss until the apples are thoroughly coated.
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15
In a large skillet, melt 3 tablespoons of the butter.
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16
Add the spiced apples and cook over moderately high heat, stirring occasionally, until they're almost tender, about 6 minutes.
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17
Scrape the apples onto a baking sheet and refrigerate until they are cool, about 15 minutes.
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18
In a medium bowl, whisk the flour with the baking soda and salt.
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19
In a measuring cup, mix the buttermilk with the Calvados and vanilla.
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20
In the bowl of a stand mixer fitted with the paddle, beat the remaining 2 sticks of butter and 2 cups of sugar with the orange zest at medium-high speed until fluffy, about 2 minutes.
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21
Add the eggs one at a time, beating well between additions.
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22
At low speed, in 3 alternating additions, beat in the dry ingredients and buttermilk mixture; scrape down the side of the bowl as necessary.
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23
Spoon the cooled apples into the bottom of the Bundt pan, spreading them out.
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24
Scrape the cake batter over the apples and smooth the surface with a spatula.
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25
Bake the cake in the center of the oven for about 1 hour, until a toothpick inserted in the center of the cake comes out clean.
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26
Let the cake cool for 5 minutes.
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27
Set a cooling rack on a baking sheet.
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28
Invert the cake onto the rack and scrape any apples stuck to the pan back onto the cake.
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29
While the apples are hot, pack the streusel topping over the top of the cake.
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30
Let stand until cool, about 1 hour.
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31
Slice the cake with a serrated knife and serve.
