Plum Buckle

Ingredients
1 1/2 cups all-purpose flour
1 tsp. baking powder
1/4 tsp. salt
16 Tbs. (2 sticks) unsalted butter, at room temperature
1 cup plus 1 Tbs. sugar
2 eggs, at room temperature
4 plums, about 1 lb. total, halved, pitted and each half cut into 4 slices
1/4 tsp. ground cinnamon

Directions

1. Position a rack in the lower third of an oven and preheat to 350 F.
   
2. Coat a 9-inch round or 8-inch square cake pan with vegetable oil spray.
   
3. Line the bottom with parchment paper and coat the paper with more spray.
   
4. In a bowl, whisk together the flour, baking powder, and salt. Set aside.
   
5. In the bowl of an electric mixer fitted with the flat beater, beat together the butter and 1 cup sugar until pale and fluffy.
   
6. Add the eggs one at a time, beating well after each addition.
   
7. Add the flour mixture and mix well.
   
8. Scrape the batter into the prepared pan and spread evenly.
   
9. Poke the plum slices into the batter, placing them close together.
   
10. In a small bowl, combine the cinnamon and 1 tbsp sugar and sprinkle over the surface.
    
11. Bake until the top is golden, the edges pull away from the pan, and a skewer or cake tester inserted into the center comes out clean, 50 to 60 minutes.
    
12. Transfer the pan to a wire rack and let cool for about 30 minutes before serving.