The Perfect Sweet Potato Cake

Sweet Potato Cake – sweet potato cake layers with toasted marshmallow filling, toasted pecan crunch and pecan buttercream.

Sweet Potato Casserole

While it’s easy for me to jump from Halloween to Christmas without skipping a beat, I really do love Thanksgiving. Thanksgiving food is some of my favorite: homemade rolls, stuffing, and sweet potato casserole. (Gimme all the carbs!).

A good sweet potato casserole is probably my most favorite dish on Turkey Day. I’ve tried a variety over the years, but my go-to version is simply made up of mashed sweet potatoes, brown sugar and toasted marshmallows and pecans.

Thinking about all those amazing flavors and textures, it only seemed fitting to throw them into a cake.

Pecan Butter Buttercream on a cake.

Sweet Potato Cake

Mastering a delicious sweet potato cake was priority number one for me. Sweet potatoes help give the cake moisture and flavor. It’s just a matter of getting the right amount.

Last year I created a butternut squash cake that was to-die-for. I roasted the butternut squash to get it nice and soft and then used about three cups of mashed squash in the cake batter. Once you add all the sugar and other ingredients, you don’t have an overwhelming vegetable flavor — just enough to hint to the butternut squash, but not so much that you think you’re eating it as a dinner side 😉

Cake on a cake stand with cake slices around it.

With a good foundation already in-hand, I decided to use the butternut squash cake as the base for this cake.

I first roasted my sweet potatoes to get them nice and soft for mashing. Once cooked, I mashed the sweet potatoes and measured about three cups (about 600 grams). It took three very large sweet potatoes to get this amount.

Because the sweet potatoes don’t have quite the same water content the butternut squash does, you’ll notice the batter for the sweet potato cake is much thicker than the butternut squash batter. Both bake up super moist!

Inside view of a cake.

Are you dying over this color?! I love how brightly colored this cake turned out just from the natural color of the sweet potatoes. It screams “Thanksgiving” to me!

Toasted Marshmallow Filling

The marshmallow filling for this was a no-brainer. I am obsessed with the toasted marshmallow filling in my Ultimate S’mores Cake. It’s inspired by a Sweetapolita recipe. I changed up the quantities a bit to include more toasted marshmallow. That idea was genius, Rosie!

Slice of cake on a plate.

Pecan Buttercream

And you know me, I love a good crunch in my cakes. Similar to my Butternut Squash Cake, I added toasted pecans between layers. I also added the toasted pecans to the buttercream, in the form of a nut butter. You guys! I think you’ll go nuts over this one (pun totally intended)!

Truly, the combination of flavors and textures in this one is a homerun, if you ask me! I hope to see it on your Thanksgiving table or next gathering. I have no doubt it will be a huge hit!

Allergy note:

I know many of you or your loved ones have nut you have to be mindful of allergies when baking. I’d hate for you to miss out on this cake because of the pecans, so here are some alternative buttercream flavors. I think would be awesome with this cake:

For the Cake

  • 3 cups (600 g) mashed sweet potatoes about three large sweet potatoes
  • 1 1/2 cup (300 g) granulated sugar
  • 5 large or extra large eggs room temperature
  • 1 cup (218 g) vegetable oil
  • 3 cups (345 g) cake flour
  • 1 tbsp (8 g) cinnamon
  • 2 tsp (8 g) baking powder
  • 1 tsp (5.6 g) salt
  • 1 tsp (3 g) nutmeg
  • ½ tsp (1.5 g) ground ginger
  • 2 tsp (8.4 g) vanilla extract

Toasted Marshmallow Filling

  • 24 large marshmallows
  • 1 cup (226 g) unsalted butter room temperature
  • 1 1/2 cups (187.5 g) powdered sugar measured and then sifted
  • 1/2 jar marshmallow fluff about 100 grams
  • 1 tsp (4.2 g) vanilla extract

Toasted Pecans and Pecan Butter

  • 2 cups (300 g) chopped pecans
  • ½ cup (100 g) granulated sugar
  • 1 tbsp (13.6 g) olive oil

Pecan Buttercream

  • 6 cups (750 g) powdered sugar measured and then sifted
  • 2 cups (452 g) unsalted butter slightly cold
  • pecan butter recipe above
  • 3 tbsp (43.3 g) heavy cream
  • *This buttercream recipe makes enough to fill and cover your cake. If you want to add additional piping, you’ll want to make an extra ½ batch.

For the Cake

  • Preheat your oven to 350 degrees F. Spray three 8-inch or four 6-inch round cake pans with non-stick spray, line with parchment and spray again. Set aside.

  • In a medium bowl, combine the cake flour, cinnamon, baking powder, salt, nutmeg, and ground ginger. Set aside.

  • In the bowl of an electric mixer fitted with the paddle attachment, beat the sugar and eggs together on medium-high speed until light and fluffy, about five minutes. Add the oil and beat on medium until combined. Add the cooled sweet potatoes and mix until combined. Add the vanilla.

  • With the mixer on low, gradually add the dry ingredients. Stir until just combined.

  • Evenly distribute the batter into the prepared pans (about 20 ounces of batter in each of the three 8-inch round pans or 15 ounces of batter in each 6-inch pan). Bake for 30 to 35 minutes, or until a toothpick inserted in the center of the cakes comes out mostly clean.

  • Let pans cool on wire racks for 10 minutes before inverting cakes onto racks to cool completely.

For the Marshmallow Filling

  • Place the marshmallows on a cookie sheet lined with parchment paper and sprayed with nonstick cooking spray. Place on the middle rack of the oven, and broil the marshmallows until golden brown on top, about 30-60 seconds. Keep your eye on them!

  • Remove the pan from the oven and gently turn the marshmallows over and broil them again until they are golden brown on the other side.

  • In the bowl of a stand mixer fitted with the paddle attachment, combine the butter and powdered sugar and beat on low until blended. Add the vanilla and mix on medium speed for about three minutes.

  • With the mixer on low speed, add the marshmallow cream and (cooled) toasted marshmallows, and mix for about one minute.

Toasted Pecans

  • Over medium heat, toast the 2 cups of pecans in the olive oil, stirring frequently. Once toasted, remove one cup of the pecans and cool them on parchment paper.

  • While the 1 cup of pecans is cooling, add the sugar to the remaining pecans and stir until the sugar is dissolved and is coating the pecans. Pour the sugared pecans over other parchment to cool and use for the filling.

For the Pecan Buttercream

  • In a food processor, combine the one cup of (non-sugared) toasted pecans with 1 tablespoon olive oil. Pulse until you’ve created a smooth nut butter.

  • In the bowl of an electric mixer, fitted with the paddle attachment, beat the butter for about 2 minutes on medium-high speed. This helps to soften the butter without the butter getting too warm by sitting on the counter half the day.

  • Add your homemade pecan butter. Mix on medium-high speed until well blended, making sure to scrape down the sides and bottom of your bowl.

  • With the mixer on low speed, gradually add the powdered sugar, followed by the cream. Turn the mixer to medium-high and beat the buttercream for about 3 to 5 minutes.

  • Before spreading on your cake, spend a couple minutes mixing the buttercream by hand with a wooden spoon to push out the air pockets.


  • Place your first cake layer, top side up on a cake board or cake plate. Spread about ¾ cup of the marshmallow filling over the cake, followed by a generous sprinkle of the toasted pecans.

  • Place the second cake layer on top of the fillings and layer with another ¾ cup marshmallow filling and more pecans.

  • Cover the entire cake with a thin coat of the pecan buttercream. This is your crumb coat. It’s not meant to be beautiful, it’s meant to be functional – so don’t spend a lot of time on this or use too much frosting. You’ll freeze the crumb coat for 10 to 15 minutes to lock in the crumbs.

  • After the crumb coat is set, continue frosting the cake with the remaining buttercream.

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