Rhubarb Coffee Cake

Ingredients

• 3 cups all-purpose flour
• 1 1/2 teaspoons baking soda
• 1 teaspoon baking powder
• 3/4 teaspoon Morton kosher salt
• 3/4 teaspoon cinnamon, (divided)
• 3 large eggs, (separated)
• 1/2 cup unsalted butter, (at room temperature)
• 2 cups sugar, (divided)
• 1 tablespoon pure vanilla extract
• 2 cups full-fat sour cream
• 2 1/4 cups thinly sliced rhubarb, (divided)

Instructions

1. 1

   Preheat oven to 350°F. Very lightly spray a 9" x 13" pan. If you want to have very clean cuts of coffee cake, line the bottom with parchment paper, letting the paper extend over the long sides of the pan. This will allow you to lift the whole cake out of the pan for slicing. If that's not a concern, just spray the pan. Set pan aside.

2. 2

   In a medium bowl, whisk together flour, baking soda, baking powder, salt, and ½ teaspoon of the cinnamon. Set aside.

3. 3

   In the bowl of a stand mixer, beat egg whites until stiff. Gently transfer whipped egg whites to a separate bowl and set aside.

4. 4

   Return same bowl to stand mixer (no need to wash the bowl first) and add the butter and 1½ cups of the sugar; cream together for two minutes. Then beat in egg yolks and vanilla.

5. 5

   Alternately mix sour cream and flour mixture into butter & sugar mixture in 2 additions each. Mix on medium speed until batter is incorporated and smooth - it will be very thick.

6. 6

   Gently fold in whipped egg whites until incorporated. Then fold in 2 cups of the rhubarb.

7. 7

   With a rubber spatula, spread batter into bottom of prepared pan, smoothing the top. Sprinkle top of batter with remaining ¼ cup of rhubarb. Then, gently press the exposed pieces of rhubarb into the batter just a bit, leaving the tops of the rhubarb pieces exposed.

8. 8

   In a small dish, combine remaining ½ cup of the sugar and remaining ¼ teaspoon of the cinnamon. Sprinkle mixture evenly over top of batter.

9. 9

   Bake for 40 to 45 minutes, or until a tester inserted into center of cake comes out clean. Remove to cooling rack to cool completely.