Place 1 cup of sliced strawberries and ¼ cup of granulated sugar in a small saucepan. Use a masher or fork to break down the strawberries into a pulp.

Heat the mixture over medium-low heat for a couple minutes while stirring frequently.

In a small bowl, combine 2 tablespoon water and 1 tablespoon cornstarch to make a cornstarch slurry. Pour into the strawberry mixture and continue to cook until it thickens like jam, about 5 min.

Pour the mixture into a bowl and place it in the fridge uncovered to cool.

Preheat the oven to 350 F / 175 C and line two large baking sheets with silicone baking mats or parchment paper.

In a large bowl or stand mixer, beat 1 cup butter and 1 cup granulated sugar on medium-high speed until lighter in color.

Mix in 3 tablespoon strawberry reduction, 1 large egg + 1 large egg yolk, 1 teaspoon vanilla extract, and a small drop of red gel food coloring on medium speed until fully incorporated.

Add 2 ½ cups flour, 2 teaspoon baking powder, and 1 teaspoon fine salt, mixing on low until just incorporated.

Scoop 2 tablespoon of strawberry reduction to the top of the dough and marble it in.

Roll scooped dough in ¼ cup granulated sugar and place on prepared baking sheets about 3 inches apart.

Bake for 10-12 minutes, until edges are set but centers are soft. Cool for 15 minutes, then move to a wire rack.

Spread strawberry reduction on top of cookies right before serving.