Step 1Start by greasing a round baking tin that fits inside your pressure cooker.
Step 2Take a bowl, and combine the softened butter and sugar until creamy and well blended.
Step 3Beat in the eggs, one at a time, ensuring each egg is fully incorporated before adding the next one.
Step 4Add the vanilla extract and mix well. In a separate bowl, sift the flour and baking powder together.
Step 5Add the dry ingredients to the butter mixture, alternating with the milk. Begin and end with the flour mixture. Mix until just combined, ensuring not overmix the batter.
Step 6Pour the batter into the greased baking tin and smooth the top with a spatula. Add 1 to 2 cups of water to the pressure cooker and place a heatproof stand or trivet inside.
Step 7Carefully place the baking tin onto the trivet, ensuring it is stable. Close the pressure cooker without the whistle and bake on medium heat for 45-50 minutes or until a toothpick inserted in the centre comes out clean.
Step 8Once cooked, remove the tin from the pressure cooker and let it cool for a few minutes before transferring the cake to a wire rack to cool completely.
Step 9Your vanilla sponge cake is ready, enjoy it.