Mom and I just made these cookies and oh my goodness they are delicious!
(Pardon the ugly colors; the combination of my camera not liking artificial light and the lemon curd from a partial opened jar makes for very little of the lemony yellow showing up.)
At first I was just planning to make a regular sugar cookie recipe for the thumbprint cookies I was craving, but since I specifically planned to use lemon curd, I looked up a recipe for that combination. We ended up using this recipe:
We were surprised to find that there was no leavening ingredient in the recipe aside from the egg, but the crumbly, shortbready texture of these cookies actually goes really well with the thick, creamy curd, and the ginger and cinnamon go so well too! The recipe has a pretty large range for the spices - 2 to 4 teaspoons of powdered ginger for a relatively small batch of cookies - so we went right in the middle with 3 tsp and I think it’s just right; the ginger is definitely present but doesn’t overwhelm the lemon. We used a jar of store-bought lemon curd rather than making our own, and it works just fine. 
Honestly, this feels like something special! Definitely appropriate for serving to houseguests or someone you want to impress! And really not hard at all!