Preheat oven to 175° C, fan. Butter and flour a 23 cm (9 inch) round cake pan with a hole in the middle.

Put frozen raspberries and ¼ cup sugar in a medium saucepan over medium heat. Bring to a simmer and cook 3-4 minutes, stirring often until raspberries are broken down and released their juices. They should look smashed.

Strain into a bowl pressing the pulp to extract as much juice as possible. Discard pulp and seeds. Set raspberry liquid aside to cool slightly.

To make the cake batter, cream butter, lemon zest and remaining 1 cup sugar until light and fluffy. Mix in vanilla extract. Add eggs one at a time, beating well after each addition.

Sift flour, baking powder and salt into a bowl. Add about 1/3 of the flour mixture to the mixer bowl. Alternate milk and flour in 2 batches, finishing with the flour.

Add ¼ cup of the cake batter to the raspberry liquid. Mix to combine.

Put 1/3 of the cake batter in the prepared cake pan. Top with 1/3 of the raspberry mixture.

Continue with another 1/3 of cake batter and a little bit more than half of the remaining raspberry mixture.

Top with the remaining cake batter and the remaining raspberry mixture.

Use a knife to lightly swirl the mixture. Don’t overdo it. You don’t want the two mixtures to mix.

Bake in the preheated oven for 45-50 minutes. Cool in pan for 10 minutes. Invert into a serving platter. Once completely cool, dust with icing sugar.