Preheat oven to 350 degrees. Line an 11x7 pan with parchment paper and spray the sides with non-stick cooking spray.
In a mixing bowl, add in the butter and almond paste. Mix until the almond paste is thoroughly incorporated into the butter. Sometimes the almond paste can be difficult to incorporate.
Add in the sugar and mix until light and fluffy.
Add in the almond extract and eggs one at a time. Mix until incorporated and then add the next egg. Scrape down the sides after each egg.
Add in the salt and flour and mix until combined.
Divide the batter into 3 equal parts.
Add red to the first bowl and green to the second bowl. Mix until combined.
If you have three 11x7 pans, spread one color evenly in each pan. If you only have one pan, spread one color into the pan. You'll have to spray it again with non-stick cooking spray and line with parchment paper for each color.
Place in the oven and bake for 12 - 13 minutes just until done. Try not to let the cakes to brown up.
Let cool for 10 minutes and slide the parchment paper with the cake on it out. Don't flip the cake out because the top will stick and become a mess.
Repeat with each cake if you only have one pan.
Once all the cakes are cooled, start adding jam to each layer. Begin with green cake. Spread a thin layer of seedless raspberry jam all over the cake. Make sure to cover all the edges and corners.
Add on the white layer of cake and repeat with jam. Add on the red cake.
Add the semi-sweet chocolate chips and shortening in a glass bowl and microwave for 30 seconds. Stir and microwave for another 30 seconds. Repeating stirring and microwaving for 30 seconds until the chocolate chips are completely melted.
Spread the chocolate chips on the red cake. You can add a little design by wiggling your spatula back and forth on the top of the chocolate.
Let set up. Cut 1-inch squares of rainbow cookies and serve. I cut off the edges, but you'll get more cookies if you leave it on.