These spring bars captured the perfect tart-sweet balance! The rhubarb filling has bright acidic notes that contrast beautifully with the buttery oat crumble creating layers of texture in every bite.
Preheat your oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
Combine oats, flour, brown sugar, salt, and cinnamon in a mixing bowl. Add melted butter and mix until crumbly texture forms, with no dry spots remaining.
Press half the crumble mixture firmly into the bottom of the prepared pan, using your fingertips for an even and compact layer.
In a separate bowl, toss sliced rhubarb with granulated sugar, lemon juice, and vanilla extract until evenly coated and juicy.
Spread the rhubarb mixture over the crust, then sprinkle the remaining crumble evenly across the top, pressing gently so some pieces stick together.
Bake for 40–45 minutes, until the top is golden brown and the filling is bubbling at the edges. Tip: Rhubarb’s tartness comes alive in spring – celebrating the season’s freshness.
Cool completely in the pan before lifting out and slicing into bars. For best texture, chill briefly before serving.