In a saucepan, bring about 2 inches of water to a simmer.

In a bowl that can sit on top of the saucepan without touching the water, add lemon juice, eggs, egg yolk, sugar, and salt. Whisk continuously over the simmering water for 10-12 minutes until thick (or until it reaches 180°F).

Remove from heat and cool to 140°F, stirring occasionally.

Cut the butter into 1-tablespoon pieces. Gradually whisk in the butter, one piece at a time, until fully melted and incorporated.

Once all butter is added, the curd will be pale yellow and thick. Cover with plastic wrap directly on the surface and refrigerate until set.

Preheat the oven to 350°F. Line two 12-cup muffin pans with cupcake liners.

Sift together flour, 3/4 cup of sugar, and salt into a medium bowl.

In a stand mixer with the whisk attachment, beat egg yolks and 1/4 cup sugar on medium speed until thick and pale yellow, about 4 minutes. Gradually add water, oil, vanilla, and almond extract, mixing well. Transfer the mixture to a large bowl.

Clean the mixer bowl and whisk. Beat egg whites until frothy. Add cream of tartar and continue beating until soft peaks form. Gradually add remaining 1/2 cup sugar and beat until stiff, glossy peaks form.

Fold the yolk mixture into the egg whites. Gradually fold in dry ingredients, about 1 cup at a time, until fully incorporated.

Divide batter among cupcake liners. Bake for about 20 minutes until golden brown and a toothpick inserted in the center comes out clean.

Cool completely on a wire rack, about 25 minutes.

Using a double boiler or a bowl over a pan of simmering water, combine egg whites, sugar, and cream of tartar. Heat, stirring constantly, until sugar dissolves and mixture is warm.

Remove from heat and beat on high speed until stiff peaks form and mixture is glossy. Add vanilla and transfer to a piping bag with a tip of your choice.

Create a 1/2-inch hole in the center of each cupcake and fill with lemon curd.

Pipe meringue frosting on top of each cupcake.

Toast the meringue with a kitchen torch until golden brown. If you don't have a torch, place cupcakes under the broiler for 1-2 minutes until golden.