Remove the butter and egg from the refrigerator and allow them to come to room temperature.
In a medium bowl, whisk together the Gluten-Free All-Purpose Flour Blend and almond flour until thoroughly combined. Set aside.
Fit your stand mixer with the paddle attachment. Beat the butter on high speed until it becomes creamy and smooth, about 1 minute.
Add the sugar to the butter and cream together until light, smooth, and fluffy.
Add the egg and mix until fully incorporated.
Add the vanilla and almond extracts, mixing to incorporate. Scrape down the sides and bottom of the bowl as needed.
Slowly add the flour mixture to the butter mixture, beating on low speed just until a very soft dough forms. Stop as soon as it comes together — tenderness is the goal.
Gently press the dough down into the bowl, cover tightly with plastic wrap, and refrigerate until firm — at least 4 hours. (Overnight is even better.)
When you are ready to bake, preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper and give it a light spray of non-stick.
Using a very small scoop, portion out about 1 tablespoon of dough and place it onto the prepared baking sheet, leaving space between each cookie. Please note: I often make these thumbprint cookies for an event, so a small cookie is just perfect for a catered event. Feel free to use a larger scoop if you prefer a larger cookie, but do note that the baking time will change with a larger cookie, as well as each individual oven.
Press your thumb or forefinger gently into the center of each cookie to create a soft indentation. This does not take much of an indention, just a small one to hold the jam.
Fill each thumbprint with about ½ teaspoon of raspberry jam. I like to use a “dash” measuring spoon and guide the jam neatly into place with a toothpick.
Bake for 6½ minutes, just until the outside edges are lightly golden brown.
Allow the cookies to cool on the baking sheet for 5–10 minutes, then transfer them to a cooling rack to cool completely.
Allow the cookies to cool for at least 30 minutes before glazing.
To Make the Glaze (If You Choose to Add It). In a small bowl, whisk together the confectioners’ sugar, 1 tablespoon of heavy cream, and vanilla until smooth and silky. Add more cream, a teaspoon at a time, until the glaze is smooth and drizzleable.
Arrange your cooled cookies in neat rows on a large baking sheet.
Transfer the glaze to a pastry bag (or a small zip-top bag with the corner snipped) and drizzle in gentle rows or criss-cross patterns, letting your hand move naturally.
Allow the glaze to set at room temperature for a couple of hours before serving or storing.