Preheat the oven to 350 degrees F and line a baking sheet with parchment paper.: As you heat the oven, notice the dry warm scent that fills the kitchen, an early signal that baking is underway. Preheating to 350 degrees F ensures the cookies start baking immediately and develop gentle lift and edge color. Lining the pan with parchment paper protects the bottoms and makes clean up easy. One common mistake is not fully preheating, which causes uneven spread and underbaked centers. If your oven runs hot, watch the first tray carefully to judge exact timing.
Add the butter and sugar-free brown sugar to a stand mixer and beat until fluffy.: You'll see the mixture lighten in color and develop a slightly airy texture, releasing a soft caramel like aroma from the sugar free brown sugar melding with the butter . This aeration builds lift and helps the cookies feel tender. Avoid over beating which can incorporate too much air and cause excessive spreading. If you do not have a stand mixer, use a hand mixer and scrape the bowl frequently to ensure even creaming.
Scrape the sides of the bowl using a rubber spatula and add the egg and vanilla and almond extracts. Beat until well-incorporated.: After scraping, add the egg and extracts so the mixture becomes uniform and glossy, with a fragrant lift from the vanilla and almond . The mixture should look smooth and slightly glossy when well combined. If you skip scraping, pockets of unmixed butter or sugar can remain, leading to inconsistent texture. Make sure the egg is at room temperature so it blends smoothly without cooling the batter.
Scrape the sides of the bowl again and add the almond flour, baking powder, and sea salt. Beat until a thick dough forms and everything is well combined.: The dough will transition from glossy to thick and sandy as the almond flour absorbs moisture, with a nutty scent becoming more prominent. Mixing just until the dough forms prevents overdevelopment and keeps the cookies tender. A frequent error is over mixing, which can make the dough dense and dry; stop when the flour is just incorporated. If your almond flour is packed, fluff it first to avoid adding too much.
Form the dough into round disc shapes and if desired, roll them in sugar-free granulated sweetener.: As you shape the dough, it should hold together and feel slightly cool to the touch from the butter . Rolling them in sugar free granulated sweetener adds a sparkling exterior and a subtle crunch that contrasts with the soft center. If the dough feels too sticky, chill briefly to firm it up; too warm dough will spread too much in the oven. Be careful not to compact the discs when shaping, or the cookies may lose lightness.
Place on the parchment-lined baking sheet at least 2 inches apart and bake for 8 to 10 minutes, or until the edges are slightly golden-brown.: As the cookies bake, watch for a light golden rim and a set center, the telltale signs they are done. You may smell a warm nutty perfume as the almond flour toasts lightly. Removing them when the edges are just turning golden prevents overbaking, which causes dryness. A common pitfall is leaving them too long; remember they continue to set as they cool on the sheet.