Preheat oven to 350°F (180°C).

For cake: In a medium bowl, whisk together sugar, melted butter, oil, and lemon zest until fluffy, 1 to 2 minutes. Add eggs, one at a time, whisking well after each addition.

In another medium bowl, whisk together flour, baking powder, and salt. In a small bowl, whisk together sour cream and vanilla. Gradually add flour mixture to butter mixture alternately with sour cream mixture, beginning and ending with flour mixture, whisking just until combined after each addition.

Spray a 6-cup charlotte cake pan with baking spray with flour. Using a pastry brush, spread any excess spray in pan, blotting brush with a paper towel as needed. Spread batter into prepared pan. Tap pan on a kitchen towel-lined counter several times to settle batter and release any air bubbles.

Bake until golden and a wooden pick inserted in center comes out clean, 30 to 35 minutes. Let cool in pan for 10 minutes. Invert cake onto a wire rack, and let cool completely.

Transfer cooled cake to a serving plate. Spread Lemon Curd onto cake.

For meringue: In the heatproof bowl of a stand mixer, whisk together sugar and egg whites by hand. Place bowl over a saucepan of simmering water. Cook, whisking frequently, until sugar completely dissolves and an instant-read thermometer registers 120°F (49°C) to 130°F (54°C).

Carefully return bowl to stand mixer. Using the whisk attachment, beat at high speed until stiff peaks form and bowl is cool to the touch, 2 to 3 minutes.

Spoon topping into a large pastry bag fitted with a ½-inch French star piping tip (Ateco #868). Pipe meringue onto cake as desired. Using a handheld kitchen torch, carefully brown meringue as desired. Best served same day as made. Refrigerate in an airtight container for up to 3 days.