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Without an image, my best guesses are either blossom end rot (at or towards the tip of the pepper) or sunburn (tends to be on the shoulder or high on the side wall). Both disorders are common during excessively hot weather as the northwest has recently had.
If it’s blossom end rot, the plant ran short of water one or several times. When that occurs, the transport of calcium is disrupted. The cells at the blossom end are weak and collapse.
If it’s sunburn, the peppers may have been exposed to excess sunlight. This can occur, if leaves are sparse, or are too small to shade the fruit.