Today’s recipe is an old family favorite, a “mainstream” recipe, which I simply tweaked a tad and converted to be gluten free, of course. It’s my much loved Gluten-Free Texas Sheet Cake.
I alluded to it a while back, but then life got busy the way it tends to do and sharing it got put on the back burner. So I’m really happy to finally be sharing this Texas Sheet Cake recipe with you today, because I think it could become a favorite in your house!
But here’s the thing, we never called this cake Texas Sheet Cake growing up. We called it Secret Cake because of its key, “secret” ingredient, which was buttermilk.
Don’t click away if you don’t use buttermilk though. While buttermilk may certainly be used, most of us make “buttermilk” using vinegar (or another sour ingredient—see recipe notes) and our milk of choice.
It was years later that I learned that Texas Sheet Cake was another name for the cake that our family would sometimes enjoy for special occasions. I kept seeing Texas Sheet Cake online, hearing the raves, and kept thinking that it looked an awfully lot like “our” Secret Cake.
I remember hearing that there were other names for this recipe as well. Maybe it’s because we live in Virginia that this cake was not Texas Sheet Cake, but Secret Cake to us and the friend who shared the recipe with us.
The original recipe came from my parents’ neighbor, Kay. I call her their neighbor because Kay was my parents’ neighbor after I’d left home and they’d built a new home.
Back when I was in college, I copied Kay’s recipe down—with a separate card for the cake itself and another one for the frosting. To show you how long ago this was, the recipe called for both Crisco and, wait for it, oleo. Oleo!
How long has it been since anyone used that word? As part of my conversion, I simply omitted the Crisco and used butter in place of that oleo. (Oleo is such a funny word to even say, isn’t it?)
This Secret Cake recipe is actually one of the first recipes that I “converted” after going gluten free and attempting to bake again. Although I had been an avid baker, I actually took about a whole year off from baking anything when I went gluten free.
There were two reasons for that. Initially, I was overwhelmed at the prospect of baking anything—well, anything that met my personal standards of tasting good with a normal, non-gritty texture.
To be clear, I’d tried both ready-made gluten-free baked goods and my own baking with purchased gluten-free all-purpose flour and the results were “not up to snuff.”
Three months into my gluten-free journey, my doctor advised that I also remove grains, dairy, sugar, soy, and a few more foods from my diet. I was showing additional sensitivities to foods and my doctor also thought that I would heal better if I removed those foods for 6 months.
While I can pretty easily create meals and bake without those ingredients now, baking anything seemed impossible at that time.
Some time soon after my very “free” period ended, I stayed gluten free, but slowly reintroduced grains, dairy, etc. and I discovered my Two-Ingredient Gluten-Free All-Purpose Flour Mix. If I want to make a gluten-free version of a recipe that calls for gluten-full all-purpose flour or simply a recipe that calls for gluten-free all-purpose flour mix, that’s my “go to” mix.
So the first time I made this cake, I used the Two-Ingredient Gluten-Free All-Purpose Flour Mix and it worked just fine. But the last two times I’ve made this gluten-free Texas Sheet Cake—for my mom’s birthday the last 2 years—I’ve included a small amount of sweet rice flour and I really love it in this recipe!
Sweet rice flour is also known as glutinous rice flour. “Glutinous” does not refer to the gluten we all need to eliminate. Instead, the “glutinous” refers to the sticky nature of the rice. And that stickiness gives this cake, which is already wonderfully moist, an amazing texture!
Really any gluten-free all-purpose flour mix will work in this recipe, but I prefer mixes that contain lighter flours and, again, love the inclusion of the little bit of sweet rice flour.
So here’s your recipe and do tell me, what do you call this cake? gluten-free Texas Sheet Cake? Secret Cake? Chocolate Sheet Cake?
Oh and one more thing, I should admit that this cake is very indulgent and that’s why I make it once a year for a crowd versus making it for just the two of us. It never disappoints for a special occasion, although the rich chocolate super sugary topping usually makes it hard to get a great photo. Tasters never complain though!
Note: Our summer family celebrations are usually held outside, on screened porches, or in garages as the entrée is always steamed crabs, which can be messy. These photos were taken in my parents’ garage.
Gluten-Free Texas Sheet Cake Recipe
Texas Sheet Cake (aka Secret Cake)
- 2 cups gluten-free all-purpose flour mix (I used 1 ¾ cups of my Two-Ingredient Gluten-Free Flour Mix and ¼ cup sweet rice flour)
- 2 cups granulated sugar
- ½ cup butter (or vegan butter or margarine)
- 1 cup water
- 3 ½ tbsp cocoa powder (or raw cacao powder)
- ½ cup buttermilk (or homemade “buttermilk”; see notes)
- 1 tsp vanilla extract
- 2 unbeaten eggs
- 1 tsp baking soda
- ½ tsp salt (I use sea salt)
- ½ cup butter (or vegan butter or margarine)
- 3 ½ tsp cocoa powder (or raw cacao powder)
- 1/3 cup buttermilk (or homemade “buttermilk”; see notes)
- 3 cups powdered sugar
- 1 tsp vanilla extract
- ½ cup chopped nuts of choice (optional)
- Preheat oven to 400F degrees.
- In a large mixing bowl, mix flour and sugar. Set aside.
- Combine butter, water, and cocoa in medium saucepan. Cook over medium to medium-high heat until mixture reaches a boil.
- Pour mixture over the flour and sugar mixture that you set aside earlier. Let stand a few minutes.
- Add buttermilk (or buttermilk substitute---see notes), vanilla extract, eggs, baking soda, and salt to the other ingredients in the mixing bowl. Mix well.
- Pour mixture into 11 x 16 jelly roll baking sheet (the one that is not only larger than a typical baking sheet, but that also has taller edges).
- Bake for about 20 minutes. Test for doneness with a toothpick.
- Add ingredients to a medium saucepan. Cook over medium to medium-high heat until mixture reaches a boil.
- Remove from heat. Stir in powdered sugar, vanilla extract, and nuts (if included).
- Pour frosting over cake hot out of the oven. Carefully spread frosting with spatula if necessary.
For ½ cup of buttermilk substitute, add 1½ tsp vinegar (I use apple cider vinegar) to measuring cup and add milk (dairy or non dairy) to ½ cup line. Let sit about 5 minutes before adding to the recipe. For 1/3 cup of buttermilk substitute, add 1 tsp vinegar to measuring cup and add milk (dairy or non dairy) to 1/3 cup line. Lemon juice can be used instead of vinegar. Cream of tartar will also work, but only half the amount is needed, so use ¾ tsp cream of tartar to make ½ cup of buttermilk substitute and use ½ tsp cream of tartar to make 1/3 cup of buttermilk substitute.
Originally published November 11, 2014; updated September 4, 2018.