This vintage raisin filling, likely passed down through generations, was used to add richness and fruity depth to cakes before the era of processed frostings. Often seen in spice cakes, oatmeal cakes, or even sandwiched between cookies, raisin filling was a staple in early American kitchens, especially around the holidays. The blend of sweet raisins, citrusy lemon, and sugar creates a deeply comforting and nostalgic bite that binds the layers of a cake with sticky, flavorful warmth.