Rainbow Cake in Jar 1 box white cake mix made according to package instructions Neon food coloring in pink, yellow, green, turquoise, and purple 3 one-pint canning jars 1 can vanilla frosting Rainbow sprinkles Preheat oven to 350 degrees. Thoroughly wash and dry the inside of each canning jar. Spray the inside of each jar thoroughly with nonstick cooking spray. Set aside. Scoop about 1/2 cups of cake batter into five small bowls. It doesn’t have to be perfect, don’t panic if you get a little more of less of one color than another. Tint each bowl of cake batter with the food coloring until very vibrant. Spoon about 3 tablespoons of the purple batter into the bottom of each jar. Spoon equal amounts of turquoise batter, then green, yellow, and pink. Place the jars in a shallow baking dish, add about 1/4″ in water in the baking dish. Place the baking dish in the oven and bake for 30-35 minutes. Remove jars and allow to cool completely before scooping a small portion from the top of your cake and adding a hefty dollop of vanilla buttercream to the top. Sprinkle & serve, or cover with a lid and store in the fridge or pop into the mail & surprise someone you love!