It’s always fun to open up my grandma’s recipe box to find the perfect dish handwritten on an index card. And her classic applesauce cake jumped out at me as the ideal treat for fall. It’s made with all the warm spices we associate with the cooler months—cinnamon, cloves, and allspice—and there are chopped walnuts and raisins for some texture. Plus, applesauce adds extra moisture, which means you’ll need slightly less butter for this recipe than many other baked goods. After making my grandma’s traditional applesauce cake, I wanted to jazz it up a bit with a modern twist. That’s when I decided to serve it with a hot rum sauce poured on top just before serving. This warm and creamy sauce is made rich and thick with a bit of cornstarch and an egg. A dash of vanilla extract adds elegant flavor, while a shot of light rum adds …