12 ounces pitted prunes
3 cups weak brewed tea (optional)
2 cups all-purpose flour
3 tablespoons unsweetened cocoa powder
4 teaspoons baking powder
1/2 teaspoon baking soda
12 tablespoons (1 1/2 sticks) unsalted butter, softened
1 1/2 cups sugar
3 large eggs
1 cup milk

In a large saucepan, cover the prunes with weak tea or water. Bring to a simmer and cook until the prunes become tender, about 30 minutes. If necessary, add more water to keep the prunes covered with liquid. Cool the prunes in the liquid, then drain it off and reserve it. Measure 2 cups of the stewed prunes and puree in a food processor. Set aside.
Preheat oven to 350°F.
Butter and flour, or line the cake pans with parchment paper.
In a medium mixing bowl, combine flour, cocoa, baking powder, and baking soda. Stir well.
In a separate bowl, combine the prune puree with the milk.
Beat together the butter and sugar until light and fluffy. Beat in the eggs one at a time, beating well after each addition. Beat in a third of the dry ingredients, then mix in half of the prune puree. Scrape the bowl. Beat in another third of the dry ingredients, the rest of the prune puree, and the remaining dry ingredients.
Divide batter evenly between the prepared pans. Bake the cakes for 30 to 40 minutes, or until a toothpick inserted into the center of the cake emerges clean. Cool the cake layers in the pans for 10 minutes before placing them onto cooling racks.