You'll love these Italian Rainbow Cookies! They feature colorful sponge cake layers made with homemade almond paste, brushed with amaretto, filled with apricot preserves and topped with melted chocolate.
Add the almond flour, powdered sugar and salt to the bowl of a food processor fitted with its blade. Use a spoon to stir the ingredients a bit.
Pulse the almond flour mixture briefly to combine further. Stop the machine to scrape down the sides with a plastic spatula as needed.
Separate the egg white from a large egg. (Store the yolk in the refrigerator for another use.) Add the egg white and almond extract to the food processor bowl. Pulse the machine again until the almond paste comes together in a ball.
Scrape out all of the almond paste from the food processor and shape it into a log. If you're not going to use the paste within an hour, place the log onto a sheet of plastic wrap. Wrap the paste tightly and then place it in a zip-top plastic bag (or double-wrap it). Refrigerate it, then let it come to room temperature before using it in the cookies.
Cake Layers (9x13)
Preheat the oven to 350 degrees F. Grease three (9x13) baking pans. After greasing them, line them with parchment paper, smoothing the paper down into the pans. Grease the tops of the parchment paper, then flour them (or use baking spray with flour).
In the bowl of a stand mixer or a large mixing bowl, add 14 ounces of room-temperature almond paste cut into slices, 1 ½ cups sugar and 1 teaspoon almond extract. Beat to combine into a crumbly mixture. Then add 1 ½ cups butter (3 sticks). Beat on low, then medium, until blended into a dough.
Add 6 large eggs and blend on low for a bit so they don't splash. Then beat on medium speed, then medium-high. Beat until the batter is smooth and creamy.
Stir ½ teaspoon of salt into 2 cups of flour. Add the mixture to the batter. Beat until it's creamy with no lumps.
Divide the batter evenly into three bowls (you can use the mixing bowl as one of them.) If you have a food scale, use it to weigh three equal amounts of batter.
Add ⅓ teaspoon of green food coloring to one of the bowls of batter. Stir to combine. Add ⅓ teaspoon of red food coloring to another bowl of batter. Use a clean spoon to stir it to combine.
Spoon the batter from one bowl into one of the prepared pans. Spread the batter evenly with the back of a tablespoon. Bake it for 10-15 minutes, until it's set and a toothpick inserted in the center comes out clean. Cool the pan on a wire rack for about 30 minutes.
While the first cake layer is baking, use a clean spatula to transfer the batter from another bowl into one of the prepared pans. Spread the batter evenly with the back of a clean tablespoon. Repeat with the last bowl of batter and your third 9x13 pan, making sure to use a clean spatula and spoon. Bake each cake layer for 10-15 minutes, as you did before. Cool each cake layer on a wire rack for 30 minutes.
When the cake layers are cool to the touch, run the tip of a knife around the sides of the pans to loosen the cake layers. Flip the green layer onto a large, flat surface that can be refrigerated, such as a large cutting board or the back of an empty baking sheet. Gently pull off the parchment paper from the cake.
Measure ¼ cup of amaretto. Brush all of it onto the cake layer, evenly. Then, use the back of a tablespoon to spread ½ cup of apricot preserves onto the cake layer.
Flip the white cake layer on top of the green layer and press down gently to make it even. Gently pull off the parchment paper from the white cake.
Measure ¼ cup of amaretto. Brush all of it onto the white cake layer, evenly. Then spread ½ cup of apricot preserves onto the cake with the back of a tablespoon.
Flip the pink cake layer on top of the white layer and press down gently to make it even. Gently pull off the parchment paper from the red cake.
Measure ¼ cup of amaretto. Brush all of it onto the pink cake layer, evenly. There is no apricot used on this layer.
Chocolate Topping
Place the chocolate chips and canola oil in a medium microwave-safe bowl. Loosely cover with wax paper and heat the chocolate and oil for 30 seconds at a time, then stir. Continue doing this until the chocolate is melted and smooth.
Immediately spread the melted chocolate on the top surface of the rainbow cake, working quickly. (Don't use chocolate on the sides.) If the chocolate in the bowl starts to harden, heat it again in the microwave for a few seconds to melt it.
Refrigerate the assembled layers until the chocolate is firm, about 30 minutes. Then, let it sit out to come to room temperature before trying to cut it, so the chocolate doesn't crack and break. Use a long, serrated knife to trim ¼ inch from all the sides and set aside for snacking, if you wish. Cut the stacked layers into rectangular cookies that are about 1 ½ inches long and 1 inch wide.
To store, place the cookies in a single layer in a container lined with wax paper. Refrigerate for up to one week or freeze for up to 3 months.
Notes
Don't worry if a cake layer breaks when you flip it. Just press it into place, and the apricot and chocolate will cover it up and hold it together. This makes about 72 cookie bars, if you cut them 1-inch wide and 1 ½-inches long.You can halve this recipe and bake the layers in three 8x8 pans.