Preheat oven to 375°. Pour melted butter into a 10-inch enamel-coated cast-iron skillet.

In a medium bowl, toss together blueberries, apricots, ¼ cup sugar, lemon zest and juice, and cinnamon.

In a large bowl, stir together flour, baking powder, salt, and remaining ¾ cup sugar. Whisk in milk until smooth. Pour mixture over melted butter in skillet. Arrange fruit over batter, placing apricots cut side up.

Bake until golden brown and a wooden pick inserted in center comes out clean, about 40 minutes.