Unlike their full-fat cousins, which get their softness from oil and butter, light cakes rely less on fat and more on sugar and liquids. More sugar minimizes the development of gluten proteins (the primary source of toughness in cakes), but it can also cause excess browning, especially if dairy products are present. Pull the cake from the oven when a wooden pick inserted in the center comes out with moist crumbs still clinging to it.
1/2 cup granulated sugar
1/2 cup packed brown sugar
6 tablespoons butter, softened
3 large eggs
1 teaspoon vanilla extract
8 ounces cake flour (about 2 cups)
1/2 teaspoon baking soda
1/4 teaspoon salt
1/4 teaspoon ground cinnamon
1/2 cup buttermilk
1/3 cup plus 2 tablespoons walnuts, toasted, chopped, and divided
1/2 teaspoon cream of tartar
3 large egg whites
3/4 cup maple sugar or granulated sugar
1/4 cup water
Dash of salt
How to Make It
Preheat oven to 350°.
Combine first 3 ingredients in a medium bowl; beat with a mixer at medium speed. Add eggs, 1 at a time, beating well after each addition. Stir in vanilla. Increase speed to high; beat for 1 minute.
Weigh flour. Combine flour and next 3 ingredients (through cinnamon), stirring well. Add flour mixture and buttermilk alternately to sugar mixture, beginning and ending with flour mixture, beating until just combined. Stir in 1/3 cup walnuts.
Place 12 muffin cup liners in muffin cups; divide batter evenly among cups. Bake at 350° for 19 minutes or until a wooden pick inserted in center comes out with moist crumbs clinging. (Cupcakes will look slightly pale.) Cool in pan 5 minutes. Remove from pan; cool on wire rack.
Place cream of tartar and egg whites in a large bowl; beat with a mixer at high speed until soft peaks form. Combine maple sugar, 1/4 cup water, and dash of salt in a small saucepan; bring to a boil. Cook, without stirring, until candy thermometer registers 238°. Gradually pour hot sugar syrup into egg white mixture, beating until stiff peaks form. Spread about 3 rounded tablespoonfuls frosting over each cupcake. Sprinkle with remaining 2 tablespoons nuts.