How to export a glare effect seperately

Hey guys, im in Cycles Blender 2.9 and Im trying to add some glow to my lights. However, I need to export this glow/bloom effect to a seperate file output. So that I have a transparant tiff/png/exr that only shows the glow effect.

I have tried connecting a output file node in the compositor…but that give me the composite image.
Can somebody tell me how the export this glare effect to a seperate file that has an alpha channel?

This is my node setup now, and the composite image with the glare effect that I need to isolate (i know it looks ridiculous atm)