Make a pistachio Bundt cake by combining 1 box of white cake mix with 1 box of pistachio instant pudding mix, 4 eggs, 1/2 cup of orange juice, 1/2 cup of water and 1/2 cup of vegetable oil. Reserve 1/4 of the batter, and pour the rest into a greased and floured Bundt pan. Mix the remaining batter with 3/4 cup of chocolate syrup, and drizzle it over the top. Bake the cake at 350 degrees Fahrenheit for one hour.
To make a rhubarb-pistachio Bundt cake with rose glaze, toss 2 1/4 cups of granulated sugar with 1/2 teaspoon of finely grated lemon zest, and then beat the sugar with 3/4 cup of butter. Once the butter turns fluffy, add 5 eggs one at a time, 2 teaspoons of rose water and 1 teaspoon of vanilla extract. In another bowl, combine 2 1/4 cups of all-purpose flour, 1/2 teaspoon of kosher salt, 1/2 teaspoon of baking powder and 1/4 teaspoon of baking soda. Alternate between adding the flour mixture and 3/4 cup of plain yogurt to the butter mixture, and stir in 3/4 cup plus 2 tablespoons of toasted and chopped raw pistachios. Add the batter and 8 ounces of sliced rhubarb in three layers to a greased and floured Bundt pan, beginning and ending with the batter.
While the cake bakes at 350 degrees Fahrenheit for 50 to 60 minutes, whisk together 2 1/2 cups of powdered sugar, 2 tablespoons of milk, 1 tablespoon of rose water, 1/2 teaspoon of vanilla extract and 1/8 teaspoon of salt for the rose glaze. Drizzle the cooled cake with the glaze followed by 2 tablespoons of dried rose petals and 2 tablespoons of toasted and copped raw pistachios.