Preheat your oven to 350°F (180°C).
In a medium bowl, whisk together 1 cup of granulated sugar, ¾ cup melted unsalted butter, ¼ cup neutral oil, and 2 teaspoons of lemon zest until fluffy, about 1 to 2 minutes.
Add 3 large eggs one at a time, whisking well after each addition.
In another bowl, whisk together 1¼ cups all-purpose flour, 2 teaspoons baking powder, and ¾ teaspoon kosher salt.
In a small bowl, whisk together ½ cup sour cream and 1 teaspoon vanilla extract.
Gradually add the dry mixture to the wet mixture alternately with the sour cream mixture, beginning and ending with the flour mixture.
Prepare a 6-cup charlotte cake pan by spraying it with cooking spray.
Spread batter into the prepared pan and tap on the counter to settle.
Bake for 30 to 35 minutes until golden and a wooden pick comes out clean.
Let cool in the pan for 10 minutes, then invert onto a wire rack to cool completely.
Transfer to a serving plate and spread with Lemon Curd.
For the meringue: In a heatproof bowl, whisk ½ cup sugar and 2 large egg whites over simmering water until sugar dissolves.
Beat at high speed until stiff peaks form.
Pipe onto the cake and brown with a kitchen torch.
Enjoy the cake same day; refrigerate leftovers for up to 3 days.