Step 1: Prepare the Cake Batter

• Cream the butter and sugar: In a large mixing bowl, cream together the softened butter and caster sugar until light and fluffy using an electric whisk.
• Add the eggs and vanilla: Beat in the eggs one at a time, followed by the vanilla extract, ensuring each egg is fully incorporated before adding the next.
• Fold in the dry ingredients: Gently fold in the self-raising flour, baking powder, and milk until you achieve a smooth batter.

Step 2: Add the Rhubarb

• Prepare the rhubarb: Chop the rhubarb into 1-inch pieces.
• Fold the rhubarb into the batter: Gently fold the chopped rhubarb into the batter, ensuring the fruit is evenly distributed throughout the mixture.

Step 3: Bake the Cake

• Preheat the oven: Preheat your oven to 180°C (160°C fan)/350°F/gas mark 4.
• Prepare the cake tin: Grease a 23cm (9-inch) round cake tin and line it with baking parchment.
• Pour the batter: Spoon the batter into the prepared tin and smooth the top with a spatula.
• Top with sugar: Sprinkle the demerara sugar evenly over the top of the cake for a crisp, golden finish.
• Bake the cake: Bake in the preheated oven for 40-50 minutes, or until a skewer inserted into the center comes out clean.
• Cool the cake: Allow the cake to cool in the tin for 10 minutes before transferring it to a wire rack to cool completely.

Step 4: Serve

• Slice and serve: Once cooled, slice the cake and serve it on its own, with a dollop of whipped cream, or even a scoop of vanilla ice cream for an extra indulgent treat.