Why You’ll Love This Recipe

I love how browning the butter transforms this cake from good to irresistible—the rich, toasted flavor seeps into every crumb. The tart rhubarb provides bright bursts, and a sprinkling of sugar on top bakes into a satisfyingly crisp crust, making it feel both homey and indulging. It’s perfect for dessert or breakfast with a cup of coffee.

ingredients

(Here’s a tip: Check out the full list of ingredients and measurements in the recipe card below.)

12 tablespoons unsalted butter (for browning)
1¾ cups all-purpose flour
¼ teaspoon baking soda
1 teaspoon baking powder
½ teaspoon salt
⅔ cup granulated sugar
2 large eggs
2 teaspoons vanilla extract
½ cup buttermilk
2 cups chopped rhubarb

For the topping:

6 tablespoons unsalted butter, at room temperature
½–¾ cup all-purpose flour
¼–½ cup brown sugar
¼ teaspoon salt
2–4 tablespoons granulated sugar (for sprinkling on top)

directions

Prep & brown butter.
I preheat the oven to 350 °F and grease a 9″ round or square pan. I melt the butter in a light‑colored saucepan, cooking until it foams, browns, and smells nutty, then remove from heat to cool slightly
Make the batter.
In a bowl, I whisk flour, baking powder, soda, and salt. Separately, I beat the browned butter with granulated sugar until combined, then add eggs one at a time and stir in vanilla. I alternate adding dry ingredients and buttermilk, starting and ending with flour, folding just until combined. Then I gently fold in rhubarb
Press into pan.
I pour the batter into the prepared pan, spreading it evenly with a spatula.
Mix crumb topping.
I combine room‑temperature butter, flour, brown sugar, and salt, rubbing with fingers until crumbly. I sprinkle the topping evenly over the batter, then dust with granulated sugar for a crunchy crust
Bake.
I bake for 50–55 minutes, until a toothpick inserted into the center comes out mostly clean and the top is tenderly golden
Cool & serve.
I let the cake cool completely so the sugar and crumbs set. I slice and serve it room temperature, or warm it slightly for breakfast or dessert.

Servings and timing

Servings: 10–12 slices
Prep time: ~30 minutes (including browning and cooling butter)
Bake time: 50–55 minutes
Total time: ~1 hour 30 minutes

Variations

I’ve stirred ground cinnamon or cardamom into the flour mix for a warm spice note
I sometimes swap half the sugar on top for coarse turbinado, which adds a deeper crunch.
For a berry twist, I mix chopped strawberries or cherries with the rhubarb before folding in
Occasionally I drizzle a simple vanilla glaze or dust lightly with powdered sugar before serving.

storage/reheating

I store leftover slices in an airtight container at room temperature for up to 2 days, or refrigerate up to 4 days. To refresh the crisp sugar top, I gently warm slices in a 325 °F oven for 5 minutes.

FAQs

Can I use frozen rhubarb?

Yes—with thawing and draining first, it works beautifully and preserves texture .

Why brown the butter?

Browning adds deep, toasted, nutty flavor that elevates the cake’s richness and complexity

Can I skip the sugar crust?

You can—but the sugar sprinkle is what gives it that signature crispy top.

How do I prevent sinking rhubarb?

I lightly toss the chopped rhubarb in a bit of flour from the dry mix before folding—it helps keep them suspended in the batter

Is it okay to bake in a springform pan?

Yes—but line it with parchment and grease well, as crumb topping can stick to the sides.

Conclusion

I adore this Brown Butter Rhubarb Cake with Crispy Sugar Top—it’s a sophisticated yet easy dessert or breakfast cake that feels like a treat. The contrast of nutty browned butter crumb and bright rhubarb is a delight, and that sweet, crunchy sugar crust makes it unforgettable. Serve it with coffee or vanilla ice cream—it never lasts long in my kitchen!