I agree with bearisgray. If you can clip the threads between and resew from the back, you could likely get your sewing machine to ease or "take up" that amount of fabric so there wasn't a pucker.
I tried to find a video but couldn't, so I'll try to explain.
If you have the side with too much fullness facing up (the red fabric), then go slowly and gently resist for a couple of stitches, while urging the top fabric under the needle. (Usually, the feed dogs will take up more fabric than that on top, but you're trying to get the machine to takeup the upper fabric by resisting the feed dogs slightly.) Little by little, the upper fabric will smooth out to match the length of the lower fabric and you'll be left with no pucker.
Wish I could show you or perhaps someone can explain it better.
Watson