Rhubarb Crumble Pie Recipe

Step 1: Prepare the Rhubarb Layer

What to do:

1. Add 3 cups of diced rhubarb to a medium saucepan along with 2 tablespoons lemon juice and ¼ cup granulated sugar. Stir it gently, and let it sit for about 5 to 10 minutes off the heat. This step helps the sugar draw out some of the rhubarb’s natural juices.
2. In a small bowl, whisk together 1 tablespoon cornstarch and 2 tablespoons water until fully dissolved—no lumps. This is important. If you skip this or leave lumps, you may end up with a starchy, gritty texture.
3. Place the saucepan over medium heat and stir in the cornstarch slurry and 1 teaspoon of vanilla paste.
4. Cook for around 5–7 minutes, stirring frequently, until the mixture thickens into a loose, glossy compote. You’re looking for a consistency similar to a warm jam—not too runny, but not fully set either. It should easily coat the back of a spoon.

What to expect:

1. As the rhubarb heats up, it will begin to soften and release more liquid. That’s normal. It shouldn’t fully break down; you want some soft chunks left for texture.
2. The mixture will go from cloudy to more vibrant as the rhubarb cooks and the cornstarch activates.

What not to do:

1. Don’t walk away while cooking. Rhubarb can scorch quickly, and the sugars will burn if left unattended.
2. Don’t boil it too hard. Keep the heat moderate to prevent the rhubarb from disintegrating into mush.
3. Set this aside to cool while you prepare the cake base and crumb topping.

Step 2: Make the Crumb Topping

What to do:

1. In a medium bowl, combine 6 tablespoons melted butter, ¾ cup + 2 tablespoons all-purpose flour, ½ cup granulated sugar, 2 tablespoons light brown sugar, and ¼ teaspoon kosher salt.
2. Stir with a fork or your fingers until the mixture clumps together. It should resemble coarse, buttery sand with some larger crumbly chunks.

What to expect:

1. The topping should hold small clumps when pressed between your fingers, but not be too greasy or wet.
2. If it’s too dry, add another tablespoon of melted butter.
3. If it’s too wet, sprinkle in a touch more flour.
4. Tip: Keep the crumble in the fridge while you prep the cake layer. Cold crumbs bake up crisper and more defined.

Step 3: Make the Cake Layer

What to do:

Cream the butter and sugars:

1. In a large mixing bowl, beat 6 tablespoons of room-temperature butter, ½ cup light brown sugar, and ½ cup granulated sugar using a hand or stand mixer on medium speed. Beat for 3–5 minutes, or until the mixture is pale, light, and fluffy. What to look for:
2. The mixture should visibly lighten in color and increase slightly in volume. If it's still dense or grainy after a few minutes, keep mixing.

Add the oil:

1. Pour in ¼ cup vegetable oil and mix again until fully incorporated. The batter will become smoother and a little more glossy.
2. Add the eggs one at a time:
3. Crack in the first egg, beat until combined, then add the second. Mix well. Add 2 teaspoons vanilla paste or extract and stir again. Important: Scrape down the sides of the bowl after each addition to make sure everything is evenly mixed.

Add the dairy:

1. Stir in ¼ cup sour cream and ¼ cup whole milk, both at room temperature. Mix until the batter becomes smooth and creamy.

Add the dry ingredients:

1. In a separate bowl, whisk together 1½ cups flour, 1 teaspoon baking powder, and ½ teaspoon kosher salt. Add the dry mix into the wet ingredients in two batches. Fold in gently with a spatula or on low speed, mixing only until the flour is just absorbed. What to expect:
2. The batter will be thick but spreadable—somewhere between a pound cake and a muffin batter.

What not to do:

1. Don’t overmix the batter after adding flour. This can cause the cake to become tough and dense.
2. Avoid cold ingredients—cold dairy won’t incorporate properly and can curdle when mixed with the butter and sugar.

Step 4: Assemble and Bake

1. Preheat the oven to 350°F (175°C) and grease a 9-inch springform pan or deep cake tin. You can also line the bottom with parchment paper for easy removal.

Layer the cake batter:

1. Spread the cake batter evenly in the prepared pan using a spatula. It will be thick—use an offset spatula or the back of a spoon to push it to the edges and smooth the top.

Add the rhubarb layer:

1. Spoon the cooled rhubarb mixture evenly over the top. Don’t swirl it into the batter—just spread it gently. It doesn’t have to cover every inch; it will spread as it bakes.

Top with crumble:

1. Sprinkle the crumb mixture generously over the entire top. Let some larger chunks fall in places for extra texture.
2. Bake for 50–60 minutes on the center rack. Start checking at the 50-minute mark. Insert a toothpick or cake tester into the center. It should come out mostly clean with a few moist crumbs—just avoid hitting a pocket of rhubarb.

What to expect while baking:

1. The crumb will turn golden brown.
2. The rhubarb may bubble slightly around the edges.
3. The cake should rise around the fruit and stay soft underneath.

Tips:

1. If the top is browning too quickly before the cake is done, loosely tent it with foil around the 40-minute mark.
2. If using a springform pan, let it cool completely before removing the sides to avoid collapse.