• Chop your rhubarb and set aside. Preheat the oven to 350°F/180°C and lightly grease a 9x9" square baking pan and line with parchment paper. Set aside.

For the Crumb

• Mix the melted butter, granulated sugar, brown sugar, and flour together in a small bowl with a spoon until crumbles form. Place in the fridge to chill.
  ¼ cup unsalted butter, ¼ cup granulated sugar, ¼ cup brown sugar, ½ cup all purpose flour

For the Cake

• Whisk the flour, sugar, baking powder, and salt together in a large mixing bowl until combined.
  1 ½ cup all purpose flour, 1 cup granulated sugar, 1 teaspoon baking powder, ¼ teaspoon salt
• Add the softened butter and beat on low with a hand mixer or stand mixer until it looks like wet sand.
  ⅔ cup unsalted butter
• Mix in the eggs and vanilla with the mixer on low.
  2 large eggs, 2 teaspoon vanilla extract
• Stream in the buttermilk as the mixer runs on low. Turn the speed up to medium and mix until smooth and well combined.
  ½ cup buttermilk
• Pour the cake batter into the prepared pan. Spread it evenly with an offset spatula or butter knife.
• Toss the chopped rhubarb and orange zest together in a medium bowl.
  3 stalks rhubarb, 2 tablespoon orange zest
• Sprinkle the rhubarb on top of the cake batter, not pressing it in.
• Generously sprinkle the crumble on top.
• Bake for 40-50 minutes until a toothpick inserted in the center comes out clean.
• Let the cake cool in the pan for 20 minutes, then pull on the parchment paper to lift the cake out of the pan. Place it on a wire cooling rack and let it come to room temperature. Dust with powdered sugar, slice, and enjoy!