Sweet Potato Honeybun Cake

This is the cake I make when I have leftover mashed sweet potato and no plan for it. Two cups of sweet potato go into the batter along with a box of yellow cake mix and a box of instant vanilla pudding, and what comes out is one of the densest, most satisfying sheet cakes I’ve made.

The sweet potato honeybun cake takes its name from the honey bun pastry — that gas station staple with the cinnamon swirl and the sweet white glaze pooled on top. This version swaps the yeast dough for a boxed cake base, adds sweet potato and pudding mix for moisture, layers in a brown sugar and cinnamon swirl, and finishes with an amber caramel glaze that sets into a lacquered top. The caramelized praline pecan bits you see scattered on the photo go on last.

The inside of this cake is dense and orange-gold. Every slice holds together. It’s exactly what a honeybun would be if it made the most of itself.

What the pudding mix is doing in there

Instant pudding mix in a cake batter is a technique that’s been in Southern baking for decades. It adds starch that keeps the crumb tight and moist longer than a standard box cake — a slice on day three tastes almost the same as a slice on day one. The vanilla flavor amplifies the sweet potato without competing with the cinnamon.

The sweet potato itself is doing double duty. It adds moisture (which means the cake stays soft without being wet) and it adds natural sugar that contributes to the deep golden-brown top you see in the photo. Don’t let that dark color alarm you partway through baking. This cake is supposed to look that way. The sweet potato and brown sugar are behind the color, not any burning.

The sour cream is the third moisture source and the one I won’t swap out. It adds fat and enough acidity to keep the crumb from going gummy. I’ve tried Greek yogurt (works). I’ve tried regular milk (don’t). The fat content in the sour cream is load-bearing here.

Four components — what matters for each

For the cake batter: the sweet potato must be completely cooled before it goes in. Hot or even warm mashed sweet potato scrambles the eggs partway through mixing and gives you a curdled-looking batter that bakes into a dense, gummy block. I bake my sweet potatoes the day before and refrigerate the mashed potato overnight. Room temperature works too — just not warm.

The yellow cake mix and vanilla pudding mix both go in dry, straight from their boxes. The pudding mix is not prepared — don’t add water or milk to it. It goes into the batter as powder and the eggs and sour cream provide all the liquid it needs.

For the cinnamon swirl: one cup of packed brown sugar and two teaspoons of cinnamon, stirred together and scattered in a layer between two halves of the batter. Swirl it with a butter knife four or five passes — just enough to create marble streaks, not enough to fully incorporate it. Over-swirling makes the brown sugar disappear into the batter and you lose the distinct layer visible in the crumb.

For the caramel glaze: powdered sugar whisked with caramel sauce, heavy cream, and vanilla. The caramel sauce is what gives the glaze its amber color — you can see in the photo that it’s not a white glaze. Jarred caramel sauce works fine. Dulce de leche works and gives a slightly richer result. Add heavy cream a tablespoon at a time until the glaze flows slowly off a whisk — not pours like water, not sits stiff like frosting.

For the praline bits: butter, brown sugar, and pecans cooked together for two minutes until the sugar caramelizes, then poured onto parchment and left to harden. They break into rough pieces that scatter over the glazed top. (I’ve made this without the praline bits when I was short on time. The cake is still very good. But the bits add a crunch that the rest of the cake doesn’t have, and they look like the photo.)

Making it — in order

Preheat to 350°F and grease a 9×13 inch baking pan. Line with parchment if you want to lift the whole slab out cleanly.

Beat the cooled mashed sweet potato, cake mix, pudding mix, eggs, oil, sour cream, vanilla, cinnamon, and nutmeg together on medium speed for 2 full minutes. The batter will be much thicker than standard cake batter — more like a thick brownie batter. This is correct. Don’t add liquid to thin it.

Pour half the batter into the pan and spread it to the edges. Mix the brown sugar and cinnamon together and scatter evenly over the surface. Pour the remaining batter on top and spread to cover the cinnamon layer completely. Then swirl: drag a butter knife through the batter in slow S-curves, about four or five passes. Stop. Put the knife down. More swirling makes the layers blend together.

Bake for 40 to 48 minutes. The top will be very dark — deep golden brown, almost mahogany at the edges. That’s the sweet potato’s natural sugar caramelizing. Test with a toothpick in the center of the pan. A few moist crumbs clinging is fine; wet batter means it needs more time. Don’t pull it out early because the color looks intense.

Cool in the pan for at least 30 minutes before the glaze goes on. The cake should feel warm to the touch but not hot — if the glaze hits a hot cake, it runs off the sides instead of setting on the surface.

Whisk the glaze until smooth and pour it over the warm cake in a slow, even stream. Use an offset spatula to pull it to the edges. It will pool slightly in the corners and set into a thin, glossy layer as it cools — exactly what you see in the photo.

Make the praline bits last: melt butter and brown sugar in a small pan over medium heat, stirring constantly, until it bubbles and smells like caramel, about 2 minutes. Add pecans, stir to coat, and pour onto a parchment-lined plate. Let it harden for 10 minutes, then break it into rough pieces and scatter over the glazed top.

A few things worth knowing

The praline bits can be made up to three days ahead. Store them in an airtight container at room temperature — they stay crunchy and are fine to add whenever the cake is ready.

The cake stores well. Covered at room temperature for two days, refrigerated for up to five. The glaze softens slightly in the fridge — leave a slice out for 15 minutes before eating and it comes back. The cinnamon swirl flavor actually deepens by day two.

On the sweet potato: canned sweet potato purée (not canned yams in syrup — plain purée) works in place of freshly mashed. Same 2-cup measurement, same instruction to make sure it’s cooled.

Serves 15 from a 9×13 pan at standard sheet cake slice size. Cut larger for fewer, more substantial slices — the cake is dense enough that smaller is often plenty.

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