Cream together 1 cup of softened unsalted butter, ½ cup granulated sugar, and ½ cup brown sugar until light and fluffy, about 2-3 minutes.

Add a pinch of sea salt, 1 large egg, and 1 teaspoon of pure vanilla extract; beat until the mixture is smooth and well combined.

Sift in 2 cups of all-purpose flour and 1 teaspoon of baking powder to the wet mixture, and gently fold until a cohesive dough forms.

Divide dough in half, incorporating ¼ cup of Dutch-processed cocoa powder into one half.

Portion out 1½ tablespoon-sized balls and roll in granulated sugar or your desired toppings.

Press an indentation into each ball using your thumb or the back of a spoon.

Place shaped cookies on a lined baking sheet, ensuring 2 inches apart, and preheat oven to 355°F (180°C).

Bake for 8-10 minutes, ensuring they are slightly firm on the edges but soft in the center.

Transfer to a wire rack to cool completely; fill indents with seedless jam or lemon curd after cooling.