Preheat your oven to 180c and lightly grease a loose bottom 20cm cake tin with vegan butter. Mix together the apple cider vinegar and plant milk, then set aside for 5 minutes.
In a large mixing bowl, cream together the vegan butter and sugar until pale and fluffy. Whisk in the milk and cider vinegar mixture and your vegan pesto!
Fold your wet and dry ingredients together and gently stir in the crushed pistachios and rose petals.
Pour your cake batter into your greased tin and bake for around 40-45 minutes then allow to cool completely.
Mix together the ingredients for the drizzle and adjust the sweetness to taste if needed. Piece a few holes in your sponge using a skewer and pour your syrup over the top.
Frost with your favourite buttercream frosting or other toppings of choice and serve!