Plum-Nectarine Buckle

Directions

1. 1
   Preheat the oven to 350F.
2. 2
   Brush a 9-inch-square cake pan or 10-inch cast-iron skillet with 2 tablespoons butter; set aside.
3. 3
   Whisk together the flour, 3/4 cup sugar, and the baking powder, allspice, and 3/4 teaspoon salt in a medium bowl; set aside.
4. 4
   Whisk together the egg, milk, vanilla, and remaining 4 tablespoons butter in another medium bowl.
5. 5
   Add the egg mixture to the flour mixture; stir to combine.
6. 6
   Spread the batter evenly into the buttered pan.
7. 7
   Toss the plums, nectarines, lemon juice, remaining 1/4 cup plus 2 tablespoons sugar, and a pinch of salt in a large bowl.
8. 8
   Spread the fruit mixture evenly over the batter.
9. 9
   Sprinkle with the topping.
10. 10
    Bake until a cake tester inserted into the center comes out with moist crumbs, about 1 hour and 15 minutes.
11. 11
    Let cool in the pan on a wire rack 1 hour before serving.