Rhubarb Cinnamon Sugar Donut Cake – A Cozy, Bakery-Style Treat at Home

Rhubarb meets cinnamon sugar in this soft, buttery cake that tastes like a classic old-fashioned donut—without the frying. It’s tender inside, crisp around the edges, and rolled in a sparkly coat of cinnamon sugar while still warm. Tart rhubarb keeps each bite bright and juicy, balancing the sweetness perfectly.

This cake is simple to make, bakes in one pan, and fills the kitchen with the best cinnamon scent. It’s the kind of dessert that vanishes slice by slice, especially with a cup of coffee or tea.

What Makes This Recipe So Good

Close-up detail: A warm slice of Rhubarb Cinnamon Sugar Donut Cake just cut from the round cake, edg

Donut-shop flavor, no deep fryer: You get that nostalgic cinnamon sugar donut taste with the ease of a single cake pan.
Perfect texture: Tender crumb, slightly crisp edges, and juicy pockets of tart rhubarb.
Balanced sweetness: The rhubarb’s tang keeps it from tasting overly sweet, even with the sugar coating.
Simple pantry ingredients: Butter, flour, sugar, eggs, cinnamon—nothing fancy or hard to find.
Great warm or at room temp: It’s lovely right out of the oven and just as good the next day.

Ingredients

For the cake:

1 3/4 cups (220 g) all-purpose flour
1 1/2 teaspoons baking powder
1/2 teaspoon baking soda
1 teaspoon ground cinnamon
1/2 teaspoon fine sea salt
1/2 cup (115 g) unsalted butter, softened
3/4 cup (150 g) granulated sugar
2 large eggs, room temperature
1 teaspoon vanilla extract
1/2 cup (120 ml) buttermilk, room temperature
1/4 cup (60 ml) sour cream or plain Greek yogurt
2 cups rhubarb, chopped into 1/2-inch pieces (fresh or frozen; if frozen, do not thaw)
1 tablespoon flour (for tossing rhubarb)

For the cinnamon sugar coating:

1/3 cup (65 g) granulated sugar
1 teaspoon ground cinnamon
3 tablespoons unsalted butter, melted (for brushing)

How to Make It

Cooking process: Overhead shot of the freshly baked cake just turned out onto a cooling rack, being

Prep the pan and oven: Heat the oven to 350°F (175°C). Grease a 9-inch round cake pan (or springform) and line the bottom with parchment for easy release.
Mix dry ingredients: In a medium bowl, whisk flour, baking powder, baking soda, cinnamon, and salt.
Set aside.
Cream butter and sugar: In a large bowl, beat the softened butter and granulated sugar until light and fluffy, about 2–3 minutes. This builds structure and helps the cake rise.
Add eggs and vanilla: Beat in the eggs one at a time, scraping the bowl as needed. Stir in the vanilla.
Combine with dairy: Mix the buttermilk and sour cream together in a small bowl or measuring cup.
Bring the batter together: Add the dry ingredients to the butter mixture in two parts, alternating with the buttermilk mixture.
Start and end with dry ingredients. Mix gently just until combined.
Fold in rhubarb: Toss the chopped rhubarb with 1 tablespoon flour, then fold it into the batter. Don’t overmix.
The batter will be thick.
Bake: Spread the batter evenly in the prepared pan. Bake 35–42 minutes, or until the top is golden, the edges pull slightly from the pan, and a toothpick comes out clean or with a few moist crumbs.
Cool briefly: Let the cake rest in the pan for 10 minutes. Run a knife around the edge, then turn it out onto a cooling rack.
Peel off the parchment.
Coat with cinnamon sugar: In a small bowl, mix the sugar and cinnamon. Brush the warm cake all over with melted butter—top and sides—then shower with the cinnamon sugar until well coated. Press lightly so it sticks.
Slice and serve: Let the cake cool another 15–20 minutes for cleaner slices, or go in while it’s still warm for that true donut vibe.

How to Store

Room temperature: Keep covered at room temp for up to 2 days.
The cinnamon sugar holds up well.
Refrigerator: Store in an airtight container for up to 5 days. Bring to room temp or warm gently before serving.
Freezer: Wrap slices tightly, then place in a freezer bag for up to 2 months. Thaw at room temp and refresh in a 300°F (150°C) oven for 8–10 minutes.
Re-crisping: If the sugar softens, a quick warm-up in the oven revives the coating.

Final presentation: Tasty of the fully coated Rhubarb Cinnamon Sugar Donut Cake on a simple white ro

Health Benefits

Rhubarb is fiber-rich: It offers dietary fiber that supports digestion and helps with satiety.
Low natural sugar in rhubarb: Rhubarb itself is quite tart and low in natural sugars, which helps balance the overall sweetness.
Calcium and vitamin K: Rhubarb contains small amounts of calcium and vitamin K, which support bone health.
Portion-friendly dessert: Because the cake is flavorful and satisfying, a modest slice goes a long way.

Common Mistakes to Avoid

Overmixing the batter: This can make the cake tough.
Mix just until the flour streaks disappear.
Skipping the flour toss on rhubarb: Lightly coating the rhubarb helps prevent it from sinking and keeps juices from making the crumb gummy.
Underbaking: The top should be deeply golden, and a tester should come out mostly clean. Rhubarb adds moisture, so give it enough time.
Coating when cold: Apply the butter and cinnamon sugar while the cake is still warm so it adheres properly.
Using cold dairy: Room-temperature eggs and buttermilk blend better and create a more even crumb.

Recipe Variations

Brown butter twist: Brown the butter for the batter, cool to room temp until solid, and proceed. You’ll get nutty, toffee-like notes.
Lemon rhubarb: Add 1 tablespoon lemon zest to the batter and a teaspoon of lemon juice to the melted butter before coating.
Whole wheat blend: Swap 1/2 cup of the all-purpose flour for whole wheat pastry flour for a heartier crumb.
Cardamom sugar: Replace half the cinnamon in the coating with ground cardamom for a Scandinavian vibe.
Gluten-free option: Use a 1:1 gluten-free baking blend with xanthan gum.
Check bake time a few minutes early.
Dairy-free: Use a neutral oil or dairy-free butter, and swap in almond milk mixed with 1 teaspoon lemon juice in place of buttermilk, plus dairy-free yogurt.

FAQ

Can I use frozen rhubarb?

Yes. Do not thaw it. Toss the frozen pieces with flour and fold into the batter straight from the freezer.

You may need to add 2–4 minutes to the bake time.

What if I don’t have buttermilk?

Mix 1/2 cup milk with 1 1/2 teaspoons lemon juice or white vinegar. Let it sit for 5 minutes, then use as directed. It won’t be as rich as real buttermilk, but it works well.

Can I make this in a loaf pan?

You can, but it will take longer to bake—about 55–65 minutes in a 9×5-inch loaf pan.

Tent with foil if the top browns too fast.

How do I keep the rhubarb from sinking?

Cut it into small, even pieces, toss with a little flour, and avoid overmixing. A thicker batter also helps suspend the fruit.

Can I reduce the sugar?

You can cut the sugar in the batter to 2/3 cup. The cake will be a bit less tender but still delicious, especially with the cinnamon sugar coating.

What other fruits work?

Strawberries pair beautifully with rhubarb.

You can also try blueberries or chopped apples, though the flavor will lean more sweet than tart.

How do I know when it’s done?

Look for a golden top, set center, and a toothpick that comes out clean or with a few moist crumbs. The cake should also spring back lightly when pressed.

Can I make it ahead?

Yes. Bake the day before, cool completely, and store covered at room temp.

If you want a freshly crisp coating, brush with butter and roll in cinnamon sugar right before serving.

Final Thoughts

This Rhubarb Cinnamon Sugar Donut Cake brings cozy bakery comfort to your kitchen with minimal fuss. It’s simple, reliable, and big on flavor, thanks to warm cinnamon and bright, tangy rhubarb. Serve it warm for the full donut effect, or save a slice for breakfast with your coffee.

Either way, it’s the kind of cake that makes any day feel a little more special.