For the cake, preheat the oven to 200C/400F/Gas 6. Grease a 23cm/9in round cake tin, and dust lightly with flour.
Warm the milk gently with the vanilla seeds until blood temperature. Pour into a bowl and stir in six tablespoons of the flour, the yeast and the sugar until well combined. Set aside in a warm place for about 30 minutes, or until has bubbles on the surface.Whisk in the beaten eggs and the lemon and orange zest.
Put the remaining flour in a large mixing bowl with the salt, then pour in the yeasted milk and egg mixture. Add the softened butter and a few drops of pink colouring, if using, and beat well until you have a sticky batter. Leave in a warm place to double in size (about 1 hour).
Meanwhile, make the sugar syrup. Heat the sugar with the orange juice and 180ml/6fl oz water over a low heat. Stir until the sugar has dissolved, then remove from the heat and add the raspberry liqueur to taste.
Once the cake mixture has doubled in size, pour it into the prepared cake tin and cover with a clean tea towel. Leave in a warm place until it has risen to three quarters of the way up the tin.
Place the cake in the preheated oven and bake for 25–30 minutes, or until the cake is golden and cooked through. Take the tin out of the oven and pour over the sugar syrup, then leave to cool in the tin.
Once the cake has cooled, turn it out onto a plate. Warm the jam with 1 tbsp water and stir to combine. Brush this over the top of the cake to glaze. Mix the strawberries with the lemon juice and icing sugar and pile some of them in the middle of the cake. Pipe or spoon the cream on top of the strawberries, then decorate the cake with the remaining strawberries and cream. Sprinkle rose petals over and around the cake, if using. Cut into slices to serve.