In a small bowl, whisk together the olive oil and brown sugar until combined. Toss starfruit in brown sugar mixture and spread evenly onto prepared baking sheet. Roast for 20-30 minutes or until edges of starfruit are golden-brown.
In a large bowl, combine rhubarb, blueberries, granulated sugar, lemon juice, and ground cinnamon. Stir gently until fruit is well coated. Spoon into prepared baking dish.
In a medium mixing bowl, stir together the flour, baking powder, and salt. Cut in butter until the mixture resembles course crumbs. Stir in brown sugar and rolled oats. Sprinkle over rhubarb mixture.
Bake in preheated oven for 40-50 minutes or until lightly browned. Let cool for 10-15 minutes before serving.
Garnish with candied starfruit and serve.
Notes
Mix it up by using strawberries, blackberries, or raspberries instead of (or in addition to) blueberries.
Try drizzling it with caramel syrup for an added dash of flavor.
Store leftovers in an airtight glass container in the refrigerator for up to 1 week.