Preheat the oven to 325°.
Place the pecans in a pie pan and roast them in the oven until they darken slightly and give off a toasted aroma, about 11 to 12 minutes. Set aside.
Place the all-purpose flour, semolina flour, baking soda, baking powder, sugar, and brown sugar in the large bowl of a kitchen mixer equipped with a paddle attachment. Mix at the lowest speed, turning on and off quickly if necessary to keep from spilling, just until the ingredients are combined—be sure to break up any lumps of brown sugar. Add the egg yolks, butter, and vanilla and mix on low until well mixed, then add the sour cream. Beat on medium speed, scraping down the sides of the bowl as necessary, until very smooth and creamy, about 2 to 3 minutes. Add the pears and pecans and stir to distribute them evenly throughout the batter.
Beat the egg whites until they form firm peaks, then gently but thoroughly fold them into the batter, turning the bowl to incorporate the whites evenly.
Spray an 8-inch by 12-inch cake pan lightly and evenly with the cooking spray. Spread the batter evenly in the pan and bake until golden brown and a knife inserted into the middle of the cake comes out clean, about 30 minutes. Cool on a rack before cutting into squares to serve.
Copyright© 2000 by Paul Prudhomme