Thimbleberry

The plant produces edible composite fruit approximately a centimeter (0.4 inches) in diameter, which ripen to a bright red in mid to late summer. Like other raspberries it is not a true berry, but instead an aggregate fruit of numerous drupelets around a central core. The drupelets may be carefully removed separately from the core when picked, leaving a hollow fruit which bears a resemblance to a thimble, perhaps giving the plant its name. (Wikipedia).