Preheat your oven to 350°F. Grease a 9-inch tart pan with a removable bottom and set aside.

In a bowl, mix together all-purpose flour, powdered sugar, and a pinch of salt. Add the cubed butter and blend until the mixture resembles coarse crumbs.

Press the mixture into the bottom and up the sides of the prepared tart pan. Ensure it is evenly distributed.

Bake the tart shell for 15 minutes or until the edges are lightly golden. Let it cool on a wire rack.

In a medium mixing bowl, whisk together sweetened condensed milk, egg yolks, and fresh key lime juice until smooth and well combined.

Pour the filling into the cooled tart shell, spreading it evenly. The filling should be thick and creamy.

Return the filled tart to the oven and bake for another 15 minutes, or until the filling is set but still slightly jiggly in the center.

Remove from the oven, let it cool to room temperature, then chill in the refrigerator for at least 2 hours before serving.

Slice the tart using a sharp knife dipped in hot water for clean cuts. Serve chilled for the best flavor.

Store any leftover tart in an airtight container in the refrigerator for up to 3 days for optimal freshness.