Melt a tablespoon of butter in a pan or microwave and using a pastry brush, brush the melted butter into the tin making sure you cover everything. Dust the tin with flour. Dusting the tin with flour will help show if you missed any bits.

Preheat the oven to gas 160 c

Cream the butter and sugar until light and fluffy.

Add the eggs one at a time, mix in well.

In a separate bowl, measure and sieve out the flour, bicarbonate of soda and salt.

Pour in the yoghurt, the extract and the lemon juice into the creamed ingredients and mix well.

Sift in the flour in a bit at a time. Mix this slowly until all the flour has disappeared.

Pour just over half the mix into the greased and floured tin. Push into any nooks and crannies! Lightly tap the tin on a hard surface to get rid of any air bubbles.

With the mixture in the tin push the raspberries in gently so they are half submerged in the mixture. You don’t want them break before they are baked. In the half left in the bowl stir in the blueberries. Add the blueberry mixture into the tin.

Bake in the centre of the oven for about 1 hour 15 minutes and until a skewer comes out clean. The best trick for seeing that is completely done is that the cake will start to pull inwards away from the metal tin when it’s done.

Leave the cake to cool before removing from the tin and placing the other way up on a cooling wrack.