2 16-ounce cans pear halves in light syrup, drained
2 tablespoons butter
2 tablespoons canola oil
3 1/2 cups sifted cake flour
1 teaspoon salt
1 teaspoon baking powder
1/2 teaspoon baking soda
1 3/4 cups sugar, divided
1 cup buttermilk
1 tablespoon vanilla extract
1 tablespoon freshly grated lemon zest
2 large eggs, separated
2 large egg whites
Puree pears in a food processor or blender. Transfer to a medium saucepan and cook over low heat, stirring almost constantly, until reduced to 1 cup, 10 to 12 minutes. (As the puree thickens and spatters less, gradually increase the heat to speed the process). Transfer to a large bowl and let cool completely.
Preheat oven to 350°F. Lightly oil a 10-inch tube pan or coat with cooking spray.
Melt butter in a small saucepan over medium heat. Cook, swirling the pan, until the butter turns a light, nutty brown, about 60 seconds. Pour into a small bowl, stir in oil and set aside.
Sift flour, salt, baking powder and baking soda into a medium bowl and set aside. Add 1 1/2 cups sugar, buttermilk, vanilla, lemon zest, egg yolks and the butter-oil mixture to the reserved pear puree and whisk until smooth. Add the dry ingredients, in two additions, folding with a whisk just until blended.
Beat the 4 egg whites in a clean mixing bowl with clean beaters until soft peaks form. While continuing to beat, slowly add the remaining 1/4 cup sugar and beat until stiff, but not dry, peaks form. Gently fold the beaten whites into the pear puree mixture with a rubber spatula. Turn the batter into the prepared pan.
Bake until a cake tester inserted in the center comes out clean, 40 to 45 minutes. Let cool in the pan for 5 minutes, then turn out onto a rack to cool, right-side up