This is a simple, excellent cake with a tender crumb, subtle spicing and soft pockets of fruit. Serve it plain, or with a dollop of ice cream or whipped cream.
Heat oven to 350 degrees. In a large bowl, whisk together flour, baking soda and salt. In a mixer bowl fitted with the paddle attachment, cream butter, sugar, vanilla, cinnamon and nutmeg. Add the egg and mix until smooth.
With the mixer on low, beat in dry ingredients until smooth (at this point the batter will be quite thick). Fold in the apples and nuts by hand.
Spread batter evenly into a greased and floured 9-inch fluted tart or quiche pan with 1-inch sides. (Alternatively you can use a 9-inch cake pan with 1-inch sides.)
Bake until cake is golden brown and a toothpick inserted in the center of the cake comes out clean, 40 to 45 minutes. Let cool 10 minutes before serving.