Cream the butter and sugar: In a large bowl, beat the softened butter and 2/3 cup sugar until light and fluffy, about 2–3 minutes. Use a hand mixer or stand mixer on medium speed.

Add egg and flavorings: Mix in the egg, vanilla, and almond extract until fully combined. If using lemon zest, add it now.

Combine dry ingredients: In a separate bowl, whisk the flour and salt. Add the dry mixture to the butter mixture in two additions. Mix on low until a soft dough forms.

Chill the dough: Cover and refrigerate for 30–45 minutes. This helps prevent spreading and makes rolling easier.

Prep the oven and pans: Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.

Shape the cookies: Scoop about 1 tablespoon of dough and roll into smooth balls. If you like a sparkly finish, roll each ball lightly in granulated or sanding sugar.

Make the “thumbprint”: Place the dough balls on the baking sheets, spacing them about 2 inches apart. Press a gentle indentation in the center with your thumb or the back of a 1/2 teaspoon measure. If the edges crack, smooth them back together.

Fill with jam: Stir the raspberry jam to loosen. Spoon about 1/2 teaspoon into each indentation. Don’t overfill or it may bubble over.

Bake: Bake for 11–13 minutes, until the edges look set and just start to turn pale golden. The cookies should remain light in color.

Cool: Let the cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely. The jam will firm up as they cool.