My original vision was lemon curd on the cookies. I decided I wanted a fruit curd with the shortbread, which is similar to what they do in Great Britain (lemon curd on shortbread and scones), but I thought it would be a new idea across the pond, especially in the midwest.
I read several articles on curd, which is a spread that was created in the area of England where marmelade also originates. My family and I used to make a lemon cheesecake with lemon curd swirl growing up that was great, so the shortbread/curd idea is a variation on that delicious theme. I wanted it to be original, and my roommate is allergic to lemon, so I tried to make a curd using concentrated pure cherry juice, using a variation on a lemon curd recipe.
My first curd recipe had way too much sugar (far left), and tasted like diet kool-aid (too sweet). I made a traditional lemon curd to compare and see if it tasted normal and thickened, which it did. I read some more articles, and deduced that you don't have to listen to anyone when you make curd.
I found that the best thing is to mix all the ingredients together completely before putting it on the double boiler, and only use a lot of sugar if you're including citrus. You should use a wooden spoon or silicon spatula, not a whisk (a whisk aerates it too much and the foam sticks around). You should keep the water heat low on the double boiler, and keep stirring until the back of the spatula and sides of the bowl are coating. You can substitute another juice flavor, but it should be combined with half lime or lemon juice and a few tablespoons of zest. I used cherry and lime. It turned out and seems to be thickening.