When I set out to make a healthy smash cake - one made with whole grain flour and free of refined sugars - the cake itself wasn't a problem. I had the perfect banana cake in mind, and it took only a little tweaking to get the recipe where I wanted it. The frosting, on the other hand, was challenging. I had a few ideas that just didn't pan out or were really underwhelming, so I took to an Internet search for inspiration. The frosting I ended up with is not only easy to make (just two ingredients!), good for you, and truly delicious - it's also an ideal pairing with the cake.
Let's start with the cake. While banana bread is its muse, it is decidedly not bread-like. I omitted the cinnamon and other spices for a clean, banana flavor with just a kiss of maple. The cake is moist but with a light crumb, so the three celebratory layers are just decadent enough and not overly heavy. As in the homemade pop tarts, I used whole spelt flour, but I imagine other flours could easily be substituted. My sweetener of choice was maple syrup, but honey would also work nicely with the recipe.
Now for the frosting. I got the idea from Peter at Souvlaki For The Soul and his banana muffins with Greek yogurt topping. To get the right consistency for a layer cake, I mixed Greek yogurt with a non-runny honey. Random: I always thought the more solid honeys were raw and/or unfiltered, but a little reading clued me in to the fact that while cooking and filtering do affect the viscosity of honey, another major factor is the type of nearby flowers. The point here is that you want a pretty solid honey so the frosting is, well, a frosting and not a glaze. Creamed honey is also an option, as is maple cream. You could always thicken it up by adding confectioner's sugar, but that was what I was trying to avoid in the first place!
Zane and my other taste-testers agree: the combination of banana cake and Greek yogurt frosting is sublime! (At least, I'm pretty sure that's what Zane would say if he could talk...) It's pleasantly sweet and the tang of the yogurt, similar to cream cheese frosting, gives it sophistication and balance. While the cake wears the role of dessert quite well, it doesn't cause a sugar crash and so can also fill in for breakfast quite nicely.
As far as decorating this cake goes, I would be a little worried that adding a generous amount of liquid food dye might negatively impact its consistency, so for a brightly colored cake consider using a gel or powdered food dye. If you keep the frosting white I would suggest using a different color plate or cake stand - I don't love how my cake ended up looking on the similarly-colored plate. I am aware of the irony of making a refined sugar-free cake and then topping it with candy sprinkles, so also don't feel like you need to follow suit from that standpoint. Aside from a non-food topper like a homemade banner, I love the idea of using edible flowers. Brightly-colored nasturtiums would be a lovely addition to this cake.
Banana Cake with Greek Yogurt Frosting
For the frosting:
2 c Greek yogurt*
1/3 c thick honey (sometimes labeled "raw" or "unfiltered") (or creamed honey, or maple cream)
For the cake:
1 1/2 c whole spelt flour (or whole wheat flour, or all-purpose flour)
1 tsp baking soda
1/4 tsp salt
3 ripe bananas
6 tbsp unsalted butter, melted and slightly cooled
1/4 c maple syrup or honey
1 egg, lightly beaten
1 tsp vanilla
1. Make the frosting. In a medium bowl, stir together the yogurt and honey until smooth. Return the frosting to the refrigerator.
2. Preheat the oven to 350 degrees F. In a medium bowl, whisk together the flour, baking soda, and salt.
3. In a separate medium bowl, mash the bananas well. Stir in the melted butter until smooth. Add the maple syrup, egg, and vanilla and stir to combine. Add the flour mixture and stir until just combined.
4. Divide the batter evenly between three buttered, 5-inch** cake pans. (I actually have only one 5-inch pan, so I baked one at a time.) Bake until a toothpick inserted in the center of the cake comes out clean, about 25 minutes. Turn cakes out onto a cooling rack until room temperature, then refrigerate for 30 minutes in preparation for frosting.
5. Place the first cake layer on your serving plate with a heaping 1/4 c of frosting, spreading it in an even layer all the way past the edges, so that some frosting hangs off the sides of the cake. Add a second layer of cake and repeat with the frosting. Top with the final cake layer and add about half of the remaining frosting. Spread the frosting evenly on the top of the cake, allowing some of it to hang or even fall a little down the sides. Using this frosting overhang, as well as the excess frosting from the middle layers, evenly coat the sides of the cake. Don't worry if it isn't perfectly frosting at this point; take a break and move the cake and the remaining frosting to the refrigerator for 15-30 minutes. Remove the cake and frosting from the refrigerator, add the remaining frosting to the cake, and evenly coat the top and sides. Return the cake to the refrigerator until an hour or less before serving.
*For a thickness more similar to a typical frosting, strain the Greek yogurt prior to mixing with the honey. Strain overnight in the fridge in a sieve lined with a double layer of cheesecloth, with a bowl underneath to catch the liquid. With this strained version, you can also add 2-3 drops food coloring, if desired.
**Makes 1 5-inch cake, although I am confident you could make this a 4-inch cake instead by adding a few minutes to the bake time.
Double the recipe and make Healthy Banana Cake Bites for your guests.
The recipe also makes 1 8-inch cake layer. Triple the recipe for a beautiful layer cake for a crowd.
The recipe also makes 10-11 cupcakes/muffins. Use 3 tbsp (or a scant 1/4 c) batter for each cupcake, and bake about 20 minutes at 350 degrees F.