A great big thank you to Meg from our Facebook community for sharing this delicious cake recipe from Epicurious!
Put oven rack in middle position and preheat oven to 375°F. Butter a 9-inch square baking pan.
Stir together 1/3 cup sugar with water, lemon juice, and cornstarch in a small saucepan, then stir in blueberries. Bring to a simmer, then simmer, stirring occasionally, 3 minutes. Remove from heat.
Whisk together flour, baking powder, salt, and remaining 1/2 cup sugar in a medium bowl.
Whisk together egg, milk, butter, and vanilla in a large bowl, then add flour mixture, whisking until just combined.
Spoon batter into baking pan, spreading evenly, then pour blueberry mixture evenly over batter (berries will sink). Bake until a knife inserted into center of cake portion comes out clean, 25 to 30 minutes. Cool in pan on a rack 5 minutes.
Cooks’ note: Cake can be made 1 day ahead and cooled completely, uncovered, then kept, wrapped well in foil, at room temperature.