Heat the oven to 180C/160C fan/ gas 4. Tip the pineapple chunks into a bowl and blitz using a hand blender until smooth. Set aside. Butter a 900g loaf tin and line with baking parchment. Beat the butter, sugar and vanilla together using a stand mixer or electric whisk until pale, light and fluffy.

Whisk the plain flour, cornflour and baking powder together in a small bowl. Set aside. With the motor on medium speed, add the beaten egg to the butter and sugar mixture a tablespoon at a time, alternating with a tablespoon of the flour mix if there is any curdling. Fold in half of the flour mix, then half the soured cream. Alternate between the remaining flour and soured cream until everything has been incorporated and the batter is light and airy. Pour into the prepared tin, then make six small gaps in the surface using the back of a lightly oiled spoon. Divide half of the blitzed pineapple between the gaps, then gently swirl into the batter using a skewer. Bake in the middle of the oven for 1 hr 15 mins, or until a skewer inserted into the middle of the cake comes out clean.

For the buttercream, beat the butter using an electric whisk or stand mixer until pale and creamy. Add the icing sugar and whisk again on low speed to combine. Add the rest of the pineapple, a tablespoon at a time, until fully incorporated. (If the pineapple is too cold, it can split the buttercream. If this happens, warm the pineapple in the microwave for 20 seconds, then whisk until spreadable.) Spread the buttercream over the cooled cake, then decorate with a few maraschino cherries. Will keep in an airtight container for three days.