Add egg and egg yolk, mixing until well combined. Add lemon juice and vanilla, mixing well.

Combine flour, baking powder, and salt in a medium bowl, stirring until combined. Add dry ingredients to wet ingredients and fold just until combined. Wrap dough in plastic wrap and chill for at least 3 hours or up to 3 days.

Meanwhile, prepare strawberry curd. Combine sliced strawberries and water in a medium sauce pot. Cover the pot and bring to a simmer over medium heat. Continue to cook until strawberries softened, about 3-4 minutes. Remove from heat and puree strawberries until smooth. Strain puree, discarding seeds.

Whisk egg, egg yolk, and sugar in a heat safe bowl. Whisk together cornstarch and lemon juice in a small bowl until cornstarch dissolves. Add cornstarch mixture to egg mixture.

Remove cookie dough from the refrigerator and portion cookies, about 2 tablespoons per cookie. Roll into balls and repeat with remaining dough. Roll each cookie dough in granulated sugar then in the powdered sugar, generously coating them. Place cookies on prepared baking sheets, placing them 2 inches apart.

Press the cookies down halfwfay with a half tablespoon measuring spoon to make an indent in the center. Fill the indent with 1 teaspoon of strawberry curd. Chill cookies in the refridgerator while oven preheats.

Preheat oven to 350 degrees F.

Bake the cookies one tray at a time for 12-14 minutes or until the edges are set and the cookies have developed a little color on the bottom. Remove from the oven and let cool on the pan for 10 minutes before transferring to a wire rack.