Ingredients
Equipment
Method
Prep and preheat
- Preheat oven to 375°F and grease an 8x8-inch baking pan so batter releases easily. A light sheen of grease should coat the corners and sides.
Mix the batter
- Whisk together all-purpose flour, sugar, baking powder, and salt in a large bowl until the mixture looks evenly speckled. Stop when no dry lumps remain.
- In a separate bowl, mix butter, melted, egg, milk, and vanilla extract until smooth and combined. The mixture should look uniform and glossy.
- Pour the wet ingredients into the dry ingredients and stir until just combined. Stop as soon as you no longer see dry flour.
- Fold in fresh rhubarb, diced gently so the pieces stay intact. You should see red-green chunks throughout the batter.
Add topping and bake
- Spread the batter into the prepared pan in an even layer so it bakes uniformly. Level the surface with a gentle shake or small taps.
- Sprinkle sugar and cinnamon evenly over the top as a crumble-like layer. The topping should cover most of the surface.
- Bake at 375°F for 30-35 minutes, until golden and a toothpick comes out clean. The edges should look set while the center springs back lightly.
Cool and serve
- Cool the cake for 10 minutes before slicing and serving warm. The crumb should firm up slightly and not look wet in the middle.
Notes
Pro tip: dice rhubarb small (about 1/2-inch) so it distributes evenly and bakes into tender, tangy bites. Store covered in the refrigerator up to 3 days and rewarm slices gently in the oven; freeze up to 1 month (wrap tightly) for best texture. For a dairy-free swap, replace milk with unsweetened almond or oat milk and use a plant-based butter in the same amount.