Preheat oven to 350 degrees F. Grease an 8-inch square baking dish with cooking spray. Set aside.: When you walk into the kitchen and set the oven to 350 degrees F , you will notice the faint mechanical hum of the oven warming. That warm-up smell is subtle but reassuring, and prepping the pan now means you can work without pausing. Lightly greasing the 8-inch square baking dish ensures the bars release cleanly later. A common mistake is under greasing, which makes removal messy, so take a moment to coat the corners. Visually, the pan should have an even sheen, not pools of oil. If your cooking spray collects droplets, wipe them with a paper towel so the dough does not slide during pressing. Doing this step first keeps your flow steady and prevents last minute scrambling.
In a medium bowl, whisk together flour, salt, and baking powder. Set aside.: As you whisk the flour , salt , and baking powder , you will hear a soft rustle and see the pale mixture become uniformly combined, which helps distribute the leavening. This blending matters because it prevents pockets of baking powder that could create odd bumps. I like to tilt the bowl and whisk in circles, watching for a consistent color and fine texture. One trouble to avoid is adding wet ingredients to unevenly mixed flour, which can yield uneven texture in the crumb. If your whisking reveals small clumps, break them up with the back of a spoon so the dry mix feels smooth and even.
In the bowl of a stand mixer, cream coconut oil and sugars on high speed until light and fluffy, about 2-3 minutes. Add the egg, vanilla extract, and coconut extract. Mix well. With the mixer on low, slowly add in the flour mixture. Mix until combined, the dough will be crumbly. Stir in the 3/4 cup coconut.: When creaming coconut oil with the sugars, you will see the mixture lighten in color and become airy, and you will hear the mixer change tone as it aerates the fat. That aeration is key for a tender crumb. After adding the egg and extracts, the bowl will smell warmly sweet, with coconut and vanilla notes surfacing. Lowering the mixer and gradually adding the dry mix prevents flour clouds and keeps the texture even. The dough will be crumbly, which is expected, and stirring in the 3/4 cup flaked coconut adds visible flecks and a slightly grainy chew. A common slip up here is overmixing, which toughens the dough, so stop as soon as the dry parts are incorporated. If the mixture seems too wet, add just a teaspoon of flour at a time to maintain a crumbly, cohesive feel.
Stir the lemon curd to loosen it up. Gently press half of dough into bottom of prepared baking dish. Evenly spread the lemon curd over dough. Sprinkle remaining dough over the top, making sure you cover the entire bars. Press gently to form the top layer. Sprinkle the additional coconut over the bars.: When you stir the lemon curd , it should move glossy and smooth, with a silky sheen that promises bright flavor. Pressing half the dough into the pan will create a uniform base, and you should feel a slight resistance as you compact it, leaving a surface that is even to the eye. Spreading the curd across that base yields a vivid, lemon yellow layer, and it should be thick enough to provide a distinct burst of flavor without seeping through. Crumbling the remaining dough over the curd will look rustic, and pressing just enough to form a top seals it in. The extra coconut sprinkled on top will toast and brown during baking. Avoid pressing so hard that you mash the curd out to the edges, which can make a soggy rim. Visually, aim for a covered but airy top, not a perfect seal.
Bake for 25 to 30 minutes or until the top is golden brown. Cool completely and cut into squares.: As the bars bake for 25 to 30 minutes , your kitchen will fill with a toasty, coconut forward aroma and the bright whisper of citrus. Keep an eye on color, watching for an even golden brown, especially at the edges. The sound is mostly quiet, but you'll notice a gentle settling as moisture evaporates and the crumb sets. Letting the pan cool completely is crucial because the lemon curd firms as it chills, allowing clean slices. Cutting too soon leads to smudged bars, so be patient. A typical pitfall is slicing hot bars, which creates sticky, uneven pieces, so wait until the bars are room temperature or even slightly chilled for neat squares.