Preheat the oven to 350 degrees F.

Line two baking sheets with parchment paper or silicone baking mats.

In a large mixing bowl, combine the lemon cake mix, eggs, vegetable oil, and lemon zest, if using. Mix until a soft dough forms and no dry streaks remain.

Use a 1½ tablespoon cookie scoop to portion the dough. Roll each portion into a smooth ball.

Arrange the dough balls on the prepared baking sheets, leaving about 3 inches between each cookie.

Bake for 10 to 12 minutes, or until the cookies are set and lightly golden around the edges.

Remove the cookies from the oven. Immediately use the back of a teaspoon measuring spoon to gently press an indentation into the center of each cookie.

Allow the cookies to cool on the baking sheet for 5 minutes, then transfer them to a wire rack.

Once slightly cooled, fill each indentation with ½ to 1 teaspoon of raspberry jam.

Cool completely before serving.