Step 1: Preheat the oven to 350°F (175°C). Grease a 9x9 inch baking dish and set aside.
Step 2: In a large mixing bowl, sift together the flour, sugar, baking powder, and salt. Stir in the melted butter until well combined.
Step 3: Add milk, beaten egg, and vanilla extract to the dry mixture. Mix until smooth.
Step 4: Fold in the raisins and suet (if using).
Step 5: Pour the batter into the prepared baking dish and bake for 40-45 minutes or until a toothpick inserted in the center comes out clean.
Step 6: Remove from the oven and let cool for at least 15 minutes before serving. Serve warm or cold with whipped cream, butter, or your favorite toppings.