What's Better Than Rainbow Cookies? Sheet Pan Rainbow Cookie Cake!

Step 1

Preheat the oven to 350°F

Step 2

Line an 18-by-13-inch sheet pan with parchment paper, spray the bottom and sides with nonstick cooking spray and set aside

Step 3

In a large bowl, make the 2 boxes of cake mix according to the package directions, adding the almond extract with the wet ingredients

Step 4

Divide the batter into three separate bowls and add food coloring to each until the desired shades of pink, green and gold are achieved (I like the look of the gold, but if you prefer, you can keep skip it and leave the third layer white)

Step 5

Pour the batter into the prepared sheet pan by pouring each color into a third of the pan, starting at the short end on the left and moving to the right (see Tip above)

Step 6

Spread out the batter, keeping the sections separate and cleaning the spatula after touching each color

Step 7

Bake the cake until a toothpick inserted in the middle comes out clean, 20 to 25 minutes

Step 8

Let cool in the pan for about 10 minutes before turning it out onto a cooling rack

Step 9

Reserve the pan and parchment paper for assembly later

Step 10

Let the cake cool completely before assembling

Step 11

To assemble the cake, use a serrated knife to cut each of the three colored sections into its own rectangle

Step 12

(This doesn't have to be perfect, and the sections can also be trimmed to your liking

Step 13

I left a little multi-color swirl on mine

Step 14

) Trim the uneven top part off of each section so it is as even as possible for stacking purposes

Step 15

Place the wire cooling rack over the sheet pan and place the red section of the cake on the rack

Step 16

This will be the bottom layer of the cake

Step 17

Spread ½ cup of the raspberry jam on top of the red layer

Step 18

Place the white/gold layer on top of the jam

Step 19

Spread the remaining ½ cup jam on top of the white/gold layer

Step 20

Place the green layer on top of the jam trimmed-side down so that the smooth side faces up

Step 21

If the cake layers are misaligned, you can trim the cake as needed with the serrated knife

Step 22

To make the ganache frosting, place the chocolate chips in a medium heatproof mixing bowl

Step 23

In a small saucepan, heat the cream over medium-high heat until it reaches a light boil, then immediately remove it from the heat so it doesn't boil over

Step 24

Pour the hot cream over the chocolate chips and whisk until completely smooth

Step 25

Let the ganache cool for about 15 minutes so it won't readily slide off the cake's surface

Step 26

Pour it slowly over the cake, letting it drip over the sides

Step 27

Use an offset spatula or other tool as needed to cover the entire cake with a smooth layer of ganache

Step 28

Let the ganache set for about 30 minutes on the counter

Step 29

(You can keep the ganache smooth and shiny by not touching it!) Transfer the cake to a plate or platter by carefully sliding two large spatulas under each side of the cake and then gently lifting and moving it

Step 30

Cut into slices and serve