In a medium saucepan, combine the strawberries, cane sugar for preserves, and lemon juice. Heat the mixture over medium heat, stirring gently until the strawberries soften and break down, about 5–10 minutes.

Remove from heat and let it cool.

In a large mixing bowl, beat together the softened unsalted butter and the sugar for the dough using a whisk until light and fluffy.

Incorporate the powdered sugar and vanilla extract, mixing until smooth.

Add the sourdough discard and egg yolk, mixing until fully incorporated.

Gradually add the all-purpose flour and salt, folding gently until just combined.

Divide the dough into two portions, shape into discs, wrap in plastic wrap, and refrigerate for about 30 minutes.

Roll out one disc on a floured surface to about 1/8-inch thickness. Cut into rectangles about 4x6 inches.

On a baking sheet lined with parchment, place a rectangle of dough and spoon a little cooled strawberry filling onto the center.

Place a second rectangle of dough over the filling, seal tightly around the edges.

Crimp the edges with a fork for decoration and seal.

Preheat oven while preparing remaining pop tarts.

Chill assembled pastries for a bit before baking.

Bake until golden brown, about 20-25 minutes. Cool on a wire rack.

Whisk together the sifted powdered sugar and milk in a small bowl until smooth.

Drizzle over cooled pop tarts and add decorating sugars if desired.