Bring water, 3/4 cup sugar, cornstarch, cinnamon, and nutmeg to a boil; stir until thickened, about 1 minutes. Reduce heat to medium and add apricots and 1 tablespoon butter. Simmer until heated through, about 5 minutes. Transfer mixture to a 9x13-inch baking dish. Combine flour, 1/4 cup sugar, baking powder, and salt in a large bowl.