Stone Fruit Slump

Slice the fruit into 10 to 12 pieces each, working over a large bowl to collect both the juices and the slices.
In a separate bowl, rub the sugar, cornstarch, and salt together. Add this to the fruit and gently toss to coat.
Gently stir in the lemon juice, then scrape the fruit and juices into a 10- to 12-inch nonreactive, deep skillet or a wide 5-quart saucepan or Dutch oven. (Whatever pan you choose, it must have a tight-fitting lid so the slump will cook all the way through.) Let the fruit mixture stand for 15 minutes. During this time, the fruit will release some of its juices and the sugar will begin to dissolve.
Bring the fruit mixture to a low simmer over medium-low heat, stirring occasionally to prevent the juice from sticking to the bottom of the pan, but do so gently to avoid breaking down the pieces of fruit. Simmer for about 2 minutes, until slightly thickened. Remove from the heat.

Whisk the flours, sugar, baking powder, baking soda, salt, cinnamon, and cardamom together in a bowl.
Add the butter and toss until evenly coated. Using your fingertips or a pastry blender, cut in the butter until pieces of dough form that are the size of peas. Add the buttermilk and stir just until the mixture comes together; it will be a slightly wet dough.
Plop the dough atop the fruit in 8 blobs, using a spoon to make the blobs and distributing the dumpling dough evenly over the surface. Return the pan to the stove top and bring to a gentle simmer over low heat. Cover the pan with its tight-fitting lid and continue simmering for 18 to 22 minutes, or until the dumplings are puffy and cooked through to the center.
Remove the cover and let cool for 15 minutes before serving. Sadly, slumps do not keep well. You’re just going to have to tuck into this immediately.