Strawberry Rhubarb Crumb Bars

Preheat the oven to 350 degrees F (175 degrees C).

Grease an 8x8-inch baking dish with butter.

Combine flour, baking soda, and salt in a bowl; stir to combine.

Mix in oats, white sugar, and brown sugar until well combined, using the back of a spoon to break up any brown sugar clumps.

Add melted butter and vanilla extract and stir well until mixture is evenly moistened.

Press 2 cups of the mixture into the prepared baking dish, pressing down lightly.

Set remaining mixture aside.

Combine strawberries and rhubarb in a bowl.

Drizzle with lemon juice and toss to combine.

Mix together 1/3 cup sugar and cornstarch in a small bowl.

Add to strawberry-rhubarb mixture and mix well.

Pour fruit filling on top of the crumb layer.

Crumble reserved crumb mixture on top of the fruit, spreading evenly.

Bake in the preheated oven until the top has browned and the filling is bubbly, about 45 minutes.

Remove and cool before cutting into bars.