Preheat oven to 350°F (180°C). Using a pastry brush, generously grease a 10 cup (2.5 litre) bundt pan with butter, taking care to reach all the creases.
In a large bowl, sift together the flour, baking powder, baking soda, and salt; set aside.
In a blender or food processor, blend ¾ cup (150 grams) of Redpath® Granulated Sugar with the black sesame seeds to a powder consistency. Whisk into the flour mixture.
Using an electric mixer or in the bowl of a stand mixer fitted with the paddle attachment beat the butter and remaining 1 cup (200 g) of Redpath® Granulated Sugar on medium speed until pale and fluffy; 4 minutes.
Add the eggs one at a time, allowing each egg to fully incorporate before adding the next.
Mix in the vanilla extract.
Reduce speed to low and alternate adding ⅓ of the flour mixture to the butter mixture, with ½ the milk, scraping down the sides of the bowl as necessary, until all ingredients are combined.
For a more dramatic black cake colour, add a few drops of black food colour to the batter and fold in.
Transfer the batter to the prepared pan and tap a few times on the counter to release any large air bubbles.
Bake until a skewer inserted into the centre of the cake emerges clean and the edges of the cake start to release from the pan; 45 to 50 minutes.
Allow cake to cool in the pan for 10 minutes before inverting onto a cooling rack and removing the pan. Allow cake to cool completely before glazing.
Place the grapes, water and lemon zest in a small pot over medium heat and bring to a simmer. Mash the grapes to release juices and allow mixture to simmer until reduced to ½ cup; about 15 minutes.
Allow grape mixture to cool for 10 minutes. Transfer to a blender and add the Redpath® Icing sugar. Blend until smooth; 3 to 4 minutes.
Pour glaze over cake and allow to dry for 15 minutes before serving.
*Black sesame seeds can be found in most Asian grocery stores, the international section of large grocery chains or natural foods stores.
*If black grapes are unavailable, use the darkest colour grapes available. The purple hue can also be boosted with a few drops of food colouring, if desired.