Consider the scenario: You cut the bell peppers in 1-2 CM squares, throw them in a pan with some oil and 1/6 teaspoon of sodium bicarbonate. You let it simmer until you get a mush.
At this point the bell pepper's peel / skin is tough to chew on.
What can you do to get the peel tender soft?
Without finding something on the internets, I'm going to boil it together with tomato sauce, diced onion, carrot, celery and minced meat for 2-4 hours and tell you how it went.
You can't. If you want a pepper puree, you have to remove the skins mechanically. Else you get a puree with "scales" of skin inside.
You also mention making a stew out of the peppers. The skins are normally not removed for a stew, just eaten along. Many people prefer to not add the pepper at the beginning, but only to throw it in for the last 15 minutes, so it doesn't overcook. This results in pepper pieces which are crisper overall, so it might not be to your taste.
If you absolutely need a stew in which the pepper is soft but there are no skins, you can probably char the pepper and peel it first, then cut up the peeled pepper and use it in the stew. But if you put it in as early as the meat, it will probably disintegrate and not be recognizable as pieces any more. If that's your goal, you can save a lot of work by mixing into your liquid ready made ljutenica (which has more vegetables and a more complex flavor profile) or pure bell pepper paste, if you can get it.
If you roast the peppers in the oven until the skin get slightly burned, then you will be able to remove it.
Then you can cut the peppers in squares and simmer to get the mush.
