Grease and line a 20 cm x 30 cm baking tin with greaseproof paper, leaving an overhang on two sides.

To make the sugar crust, put the rosemary, orange zest, vanilla seeds and two tablespoons of the sugar into a mortar and pound until the mix resembles wet sand and smells deeply fragrant (alternatively, simply rub them all together with your fingertips).

Stir in the remaining tablespoon of sugar and set aside.

Heat the oven to 190C (170C fan)/375F/gas mark 5.

Put the caster sugar and orange zest in the bowl of an electric mixer fitted with a paddle attachment, then rub with your fingertips until fragrant.

Add the butter and beat on medium-high for about two minutes, until light and creamy.

Add the eggs one at a time, beating well after each addition and scraping down the sides of the bowl as required, then beat in the vanilla.

In a second bowl, whisk the flour, baking powder, baking soda and salt.

With the mixer on low speed, add the dry ingredients and soured cream to the batter alternately in two or three stages, beginning and ending with the flour mixture.

Scrape down the bowl, then mix briefly until smooth and evenly combined.

Scrape the batter into the lined tin and smooth out the surface.

Arrange the apricots cut side up on top, without overlapping.

Sprinkle evenly with the rosemary-orange sugar and bake for 40-45 minutes, or until a skewer inserted into the centre comes out clean.

Remove and leave to cool in the tin for 15 minutes, then transfer to a rack.

Serve warm or at room temperature with pouring cream.