Blueberries pair beautifully with stone fruits such as nectarines, peaches, and apricots. This simple dessert goes together in minutes, with a crumble topping that's healthier than the usual butter-based streusel. Serve warm with a scoop of frozen vanilla yogurt, or try our Blueberry Gelato for a perfect accompaniment.
Position a rack in the lower third of the oven and preheat to 375 degrees F.
Place the blueberries and nectarines in a medium-size bowl. Add the cornstarch and brown sugar, and toss to coat the fruit. Transfer the mixture to an 8-inch square baking pan.
To make the topping, place the flour, oats, sunflower seeds, sugar, and cinnamon in a small bowl and whisk to blend. Add the maple syrup and the oil, and stir to combine. Sprinkle the topping over the fruit in the baking pan, but don't pack it down.
Bake the crisp until the juices bubble around the edges of the pan and the topping is brown and crisp, 30 to 45 minutes. Serve warm.