Maple Walnut Cake

Ingredients

• 1 tablespoon vegetable oil
• 3 tablespoons all purpose flour
• 2 cups sifted all-purpose flour
• 2 teaspoons baking powder
• ½ cup vegetable oil
• ¾ cups brewed coffee, cold
• 4 teaspoons pure maple extract
• 7 large eggs, seperated and at room temperature
• 1 ½ cups (packed) light brown sugar
• 1 cup granulated sugar
• 1 ¼ cups toasted walnuts, finely chopped
• Powdered sugar (optional)