Blueberry-Lemon Icebox Cake

For the blueberry sauce:

fresh blueberries, plus ⅓ cup, divided

granulated sugar

water

juice of ½ a large lemon (about 1 tablespoon)

For the lemon cream:

mascarpone cheese, room temperature

powdered sugar

zest of 1 large lemon

heavy whipping cream

store-bought or homemade lemon curd, divided

9x5 pound cake, trimmed of top, bottom and sides (saved for another use)