Add the gluten-free flour, xanthan gum, baking powder, baking soda, and salt to a medium bowl. Whisk to combine. Set aside.
Add the granulated sugar and lemon zest to the bowl of a stand mixer. Use your hands to rub the zest into the sugar to release the natural oils. Add the butter and cream together with the sugar for two minutes on medium-high speed. Scrape down the bowl and beat in the eggs one at a time. Add the ricotta cheese, vanilla extract, almond extract, and lemon juice. Mix to combine, scraping down the bowl as needed.
Add the dry ingredients to the wet ingredients and mix on low until fully incorporated. Cover the bowl with plastic wrap and refrigerate for 6 hours or overnight.
Preheat the oven to 350°F and line 2 half sheet pans with parchment paper or silicone baking mats.
Portion the cookie dough with a 1-tablespoon scoop and drop the dough onto the prepared baking sheets, leaving about 2 inches between each cookie. Bake the cookies for 12 minutes or until the bottoms are slightly golden. Repeat with remaining cookie dough, cooling the baking pans completely between each batch.
Cool the cookies on the baking pan for 5 minutes then transfer to a wire rack to cool completely.
Once the cookies are cool, make the glaze by mixing the powdered sugar and lemon juice together. Dip each cookie in the glaze and top with a sliced almond or lemon zest and let the glaze set.
Notes
The cookie dough can be refrigerated up to 3 days before baking. Store the cookies at room temperature in an airtight container up to 2 days or refrigerate up to1 month.