yay you! Peppers and tomatoes change after a bit of cooking to soft squidgy and much stronger flavour. If you cook for less time you don't get that change so much. It's a preference thing, some like to avoid the squidgy, some like the stronger flavour. Nice thing about cooking for yourself is you get to choose.
The length of time depends on heat, so hotter is faster. The pan fried method mentioned above would probably be the quickest. I prefer to put in the oven because I like to have a little sit down and anticipate my dinner which is "cooking itself" in the oven
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I would slice the peppers lengthways because you get more of the filling exposed so can add more cheese on top (always good) and you get a bigger variation in textures, crunchy top, soggy bottom, juicy middle.
All way more information about my relationship with stuffed peppers than anyone needs