2 eggs, separated
1/2 cup butter, softened
1 cup packed brown sugar
2/3 cup milk
1/2 teaspoon vanilla extract
1 1/2 cups cake flour
1 1/4 teaspoons pumpkin pie spice
1/2 teaspoon baking soda
1/4 teaspoon cream of tartar
1/4 cup sugar
1/4 cup ground pecans

Place egg whites in a mixing bowl; let stand at room temperature for 30 minutes. Meanwhile, in another mixing bowl, cream butter and brown sugar. Add the egg yolks, milk and vanilla; mix well.
Combine the flour, pumpkin pie spice and baking soda; add to the creamed mixture until combined. Fill paper-lined muffin cups half full. Bake at 350 degrees F for 20 minutes.
Add cream of tartar to egg whites; beat on medium speed until soft peaks form. Gradually beat in sugar, 1 tablespoon at a time, on high until stiff peaks form and sugar is dissolved. Fold in nuts. Spread about 2 tablespoons over each cupcake.
Bake 11-12 minutes longer or until golden brown and a toothpick inserted into cupcake comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.

Source: allrecipes.com