When measuring flour, we spoon it into a dry measuring cup and level off the excess. (Scooping directly from the bag compacts the flour, resulting in dry baked goods.) If you can’t find roasted unsalted pecans, bake raw pecans on a baking sheet in a 350-degree-F oven for 7 to 8 minutes. You can freeze the unfrosted cake layer wrapped in plastic and then foil for up to 2 months. Thaw it in the refrigerator. You can refrigerate the frosting in an airtight container for up to a week.