Well i have to say that is how a dish should be critiqued! Great help with the pics of all the stages.
Did you chop your onion/pepper mix finely enough as it looks quite large from the pics?? The pieces should be just a few mm by a few mm thus only need a few minutes to cook. They should have a bite to them whilst not being overpowering. I Do not get an over riding taste of the peppers as they cook out quite quickly due to the size.
I have looked over my recipe wondering if my instructions have led you down the wrong route. I have came up with:
1. I probably reduce more of the gravy at the start on a higher heat, more towards 200ml
2. Onion/pepper is more finely chopped
3. cooking time. Usually only 4-5 mins for second reduction stage. 10 mins seems a long time to reduce down 150ml gravy??? Is your gas high enough?
4. The half onion should not really have a bite to it as can be raw tasting. Needs to be just wilting.
I think leaving the half onions possibly until the start of the second reduction will give you the results BUT for curries I am used to from local TA, the onion pepper must be very finely chopped and only cooked out for 5 mins on a highish heat.
I know unkle frank was going to try this so after his feedback I will make this again next week and try to find out where the dish may have gone wrong for you

Thanks for feedback
Regards
Barry