Prune Upside Down Cake with Toffee and Sesame

For sesame-prune layer, line 9-inch round cake pan with parchment paper and lightly grease with nonstick cooking spray.

In large, non-reactive saucepan over low heat, combine brown sugar, butter, vinegar, orange zest, vanilla and salt. Stir mixture gently with heatproof spatula until butter melts. Increase heat to medium; using wire whisk, whisk mixture until it becomes cohesive and looks like caramel. Allow caramel to simmer gently 1 minutes.

Stir in sesame seeds to combine and immediately pour into bottom of prepared pan, tilting pan so caramel coats it evenly. (Caramel thickens rapidly as it cools, so do this quickly while it’s still warm.)

Place prunes in a decorative pattern over caramel, pressing gently into caramel layer. Cool completely.

For cake, preheat oven to 350 F. In medium non-reactive saucepan, melt butter over medium heat. Cook gently until it begins to smell fragrant and nutty and begins to brown, stirring frequently. Remove from heat and cool completely.

Meanwhile, in large bowl, combine flour, baking powder, baking soda and salt; set aside.

In stand mixer bowl, cream cooled butter and brown sugar with paddle attachment until light and fluffy. Add eggs, one at a time; mix until just combined, scraping down sides. Add orange zest and juice, olive oil and vinegar; mix just to combine.

Scrape batter into pan over caramel layer, leveling so it covers caramel completely and evenly. Bake 45 to 45-50 minutes, rotating the pan once halfway through baking. When cake is done, it should be an even deep golden brown and spring back lightly when pressed in center. Allow cake to cool 10 minutes (if you let it cool much longer, the caramel portion will stick to the bottom of the pan when unmolding). Using a knife, gently separate edges of cake from pan.