Brown sugar-buttermilk snack cake with blackberries and caraamel

Directions:
1. Position a rack in the middle of the oven. Preheat the oven to 350 degrees. Coat an 8-inch square pan with nonstick spray.

2. Whisk together the flour, baking soda, and salt in a medium bowl to aerate and combine; set aside.

3. In the bowl of a stand mixer, beat the butter with the flat paddle attachment on medium-high speed until creamy, about 1 minute. Add the brown sugar and beat until light and fluffy, about 3 minutes, scraping down the bowl once or twice. Beat in the egg until well combined. Add the flour mixture in two additions, alternately with the buttermilk. Begin and end with the flour mixture and beat briefly until smooth. Scrape the batter evenly into the pan and smooth the top with an offset spatula. It will be a fairly shallow layer. Scatter the blackberries evenly on top, reserving about 5 of them; do not press into the batter, as they will sink during baking.

4. Bake for 15 to 25 minutes, or until a toothpick inserted in the center shows a few moist crumbs when removed. The cake will just have begun to come away form the sides of the pan. Cool in the pan on a rack before decorating.

5. For the icing, combine the brown sugar, butter, and cream in a small saucepan and bring to a simmer over medium-high heat. Simmer for 1 minute, whisking frequently. Remove from the heat and whisk in the confectioners' sugar and vanilla until smooth and fluid. It will firm up very quickly, and if you whisk or cool it for too long, it will become too firm and sugary. Use a spoon to immediately drizzle about half the icing all over the top of the cake, then quickly sprinkle the walnuts and reserved berries evenly over the top while the icing is still wet. Drizzle with the remaining icing, which will set up almost immediately, and serve. Store at room temperature, well wrapped in plastic warp for up to 1 day.