Preheat oven to 325 degrees and lightly spray a 9 inch baking pan with nonstick cooking spray. In a large bowl, beat the eggs, butter and olive oil with an electric mixer for 30 seconds until the mixture becomes thick. Add the dry mix and lemon zest and mix until thoroughly combined, scraping down the sides of the bowl at least once.

Pour the cake batter into the prepared pan and bake about 40 minutes until the top is golden and a toothpick inserted in the center comes out clean. Cool the cake for 10 minutes then remove cake from the pan and cool it completely on a wire rack.

To make the topping, beat heavy whipping cream until stiff peaks form; set aside. In a medium bowl, mix the mascarpone, sugar, salt and lemon zest. Gently fold the whipped cream into the mascarpone mixture and whip lightly until well combined.

Spread mascarpone whipped cream on top of the cooled cake. Garnish with sliced plums and drizzle with honey.