1. Preheat your oven to 170C.
2. Sift together the flour, baking powder, baking soda and salt into a large bowl.
3. Into the large mixing jug of your Triblade System Pro, add all of the other ingredients and using the Triblade mixer fitted with the balloon whisk, thoroughly combine the wet ingredients.
4. Add the wet ingredients to the dry and carefully mix with the whisk on the lowest speed. Once the mixture is combined, pour into a parchment lined loaf tin and bake in the preheated oven for 1 hour, until a skewer inserted into the middle of the loaf comes out clean.
5. Whilst the cake is still hot from the oven, mix together the granulated sugar and thyme leaves, so that the leaves get a bashed about, then add the grapefruit juice and mix together.
6. Poke holes into the cake using a skewer, then tip the grapefruit juice and sugar mixture over the cake, spreading it all over.
7. Scatter the top with thyme sprigs and rose petals. Leave the cake to cool in the tin and allow the syrup to soak into the cake and dry to create a crunchy topping.