I grew up on Long Island, New York, where many delis, bakeries, and bagel shops include rainbow cookies among a variety of other pastries and cookies. Incidentally, rainbow cookies are closer to being chocolate covered mini-cakes than they are to being cookies. The combination of almond paste, raspberry jam, and chocolate is irresistible – all of it packed into one layered bite-sized flavor bomb.
The recipe in Saveur is excellent – on the first attempt I came out with perfect cookies that tasted delicious. The process was time consuming though, primarily because we have just one 9×13 baking pan. Because of this, I had to bake each of the three cake layers separately. I highly recommend you use three baking sheets and bake everything in the oven all at once to cut down on cooking time.
Two other things to note: the batter for the cookie mix is not so easy to spread in the pan. Be patient as you do this. Your patience will be rewarded. The second thing to note is that I had to bake the cake sheets for closer to 20 minutes before they started to brown. Monitor your cakes carefully and don’t be surprised if 10 minutes isn’t enough time. (It could also be that my oven’s temperature isn’t as consistent, which may have resulted in the longer baking time).
Try following the recipe as it’s written, and adjust baking time as needed. Here are pictures showing each step of the process once the cake sheets are done: