Yield: 16 small bars, as shown, or 8 large ones; recipe can be doubled and baked in a 9×13-inch baking pan, where they will come out a little thicker

• 1 cup (80 grams) rolled oats
• ¾ cup (95 grams) plus up to 2 tablespoons (15 grams) extra all-purpose flour
• ½ cup (95 grams) light brown sugar
• Heaped ¼ teaspoon table salt
• 6 tablespoons (85 grams) unsalted butter, melted
• 1 teaspoon cornstarch
• 1 tablespoon (15 ml) lemon juice
• 1 tablespoon (15 grams) granulated sugar, divided
• 1 cup (125 grams) small-diced rhubarb (from about 1 ½ medium stalks)
• 1 cup (155 grams) small-diced strawberries
• Powdered sugar, for decoration, if desired

Heat oven to 375 degrees F. For easy removal, line bottom and two sides of 8-by-8-inch square baking pan with parchment paper.

Mix oats, ¾ cup flour, brown sugar and salt in a medium bowl. Pour melted butter over, and stir until clumps form. If the clumps feel soft or look overly damp, add the remaining 2 tablespoons flour. 

Set aside ½ cup of the crumble mixture. Press the rest of the crumb mixture evenly in the bottom of the pan.

Toss fruit with cornstarch and lemon juice. Spread half the fruit over the crust. Sprinkle it evenly with ½ tablespoon of granulated sugar. Spread remaining fruit over this, and top with second ½ tablespoon sugar. Scatter reserved crumbs over fruit and bake bars for 30 to 40 minutes (firmer fruits will take longer), until fruit is bubbly and crisp portion is golden and fragrant.

Cut into squares and sprinkle with powdered sugar before serving. Store leftovers in fridge.