Make the cream cheese filling by combining cream cheese, lemon juice, and confectioners' sugar until thoroughly mixed. Scoop twelve 1-teaspoon balls onto a baking sheet lined with wax paper and freeze until solid.

Toss diced strawberries with cornstarch in a small bowl and set aside.

In a large bowl, whisk together flour, baking powder, baking soda, and salt; set aside.

Cream together butter and sugars in the bowl of your mixer. Beat on low speed for 3 minutes until smooth and creamy. Gradually add egg and vanilla, mixing on low until combined.

Stir in the flour mixture, then fold in the diced strawberries. Freeze the cookie dough for 30 minutes or refrigerate for 1 hour.

Once chilled, form the cookie dough balls using 2 tablespoons of dough each. These cookies will be tall. If the dough balls lose firmness while shaping, return them to the freezer to regain solidity.

Preheat the oven to 350°F. Place the dough balls onto a baking sheet lined with parchment paper or a baking mat, ensuring 2-3 inches of space between each ball as they expand while baking.

Using a cookie scoop, remove approximately 1 to 1 ½ teaspoons of dough from the top center of each cookie ball, leaving the edges slightly raised. Place the removed dough nearby for use in the next step. The cavity should be large enough to hold the frozen cream cheese balls.

Remove the cream cheese balls from the freezer. Insert one frozen cream cheese ball into the center of each cookie dough ball, then cover it with the reserved dough, pinching the edges to seal the cream cheese inside. If the dough becomes sticky, refreeze the balls until firm before baking.

Bake for 14-16 minutes, adjusting for oven variations. Allow the cookies to cool completely before serving.