Q.what causes black blemish on growing red bell peppers
What causes black blemish on growing red bell peppers?

Certified GKH Gardening Expert
If the spot or blemish is on the top or sides of the fruit, then it is likely sunscald and is from too much direct sunlight. A simple shade will help stop it. If it's on the bottom of the fruit, then it is blossom end rot. These articles will help: https://www.gardeningknowhow.com/edible/vegetables/pepper/pepper-sunscald.htm
https://www.gardeningknowhow.com/edible/vegetables/pepper/pepper-blossom-end-rot.htm