Preheat your oven to 350°F. Grease and flour two 9-inch round cake pans.
Cream together the softened butter and granulated sugar until light and fluffy, about 3-5 minutes. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
In a separate bowl, whisk together flour, baking powder, and salt. Gradually add to the wet ingredients, alternating with milk. Mix until just combined.
Divide the batter between the prepared pans and bake for 25-30 minutes. Let cool in pans for 10 minutes before transferring to wire racks.
For the lemon curd, combine lemon juice, zest, and cornstarch in a saucepan over medium heat. Stir until thickened, about 5-7 minutes. Let cool.
For the meringue, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar and beat until stiff peaks form.
Assemble the cake by placing one layer on a serving plate, spreading lemon curd on top, adding the second layer, and topping with whipped cream and meringue.
Brown the meringue with a kitchen torch or under the broiler for a few minutes.