Rainbow Cake in Jar
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!
POST EDIT: Several commenters have indicated that the cake is not cooking all the way through in the 30-35 minutes indicated in the recipe. This was enough time for our cake, but I’m cooking at high altitudes, and my oven tends to bake hot. So, I’d recommend baking the cake for 40 minutes, then return it to the oven if it still doesn’t spring back to the touch when you check to see if it’s finished. As for the cake puffing up and out of it’s bottle, ours did that a bit, as well. Easy fix. We just scooped a bit of the cake out to make room for the frosting and wiped the outside of our jars clean. Several people have indicated that the wide-mouthed mason jars work a little better for this purpose. I’ve not yet baked with wide-mouthed. What you see above is what was baked in my kitchen according to the recipe instructions, and what came out of the oven when it was all. Of course, if you’re feeling wildly impatient, you can also zap the cake in the microwave for 2 minutes. It’s going to bubble up, for sure, but you can scoop the top part of that cake out, frost it, and no one will ever be the wiser. Good luck, everyone! This is such a fun cake. My kids went nuts over it, and I hope it works as beautifully for you as it did for us!