Blueberry Donuts

"These delicious Blueberry Donuts are soft, cake-baked donuts with blueberries and cinnamon, dunked in an easy 3-ingredient glaze. Homemade donuts are so much fun and so tasty. Mix the batter just until combined. Overmixing the batter can overactivate the gluten, making doughnuts gummy and tough. Use a large piping bag or a gallon storage bag with a corner cut off to pipe the batter into the greased donut cavities. Bake the donuts just until set and lightly browned. You can use the toothpick test. Insert a toothpick in the thickest part of the donut. If it comes out clean or with a few moist crumbs, but no wet batter, they’re ready."