Preheat the oven to 325°F. Grease and flour a 13x9-inch baking pan, then set it aside.
In a large mixing bowl, combine sugar, olive oil, eggs, milk, lemon juice, and lemon zest.
Use a hand mixer to beat the mixture for about 2 minutes, until it becomes slightly pale in color.
Sift in the flour, baking powder, baking soda, and salt, then gently fold them into the wet ingredients until fully combined and no flour remains.
Pour the batter into the prepared baking pan and use a rubber spatula to spread it evenly.
Bake the cake in the preheated 325°F oven for 25–30 minutes, or until a toothpick inserted in the center comes out mostly clean with a few crumbs.
Allow the cake to cool completely before starting the frosting.
In a bowl, whip together mascarpone, powdered sugar, lemon juice, and lemon zest until just combined.
Add the heavy cream and whip until stiff peaks form. Be careful not to overmix, or the frosting may clump and curdle.
Spread the frosting evenly over the cooled cake. Serve with fresh berries if desired.
Store leftovers in an airtight container or cover the pan with a lid and refrigerate for up to 3 days to keep the cake fresh. Enjoy!
