Your exposures are all over the place. Your camera was in Aperture Priority mode set to f/36. The first image I looked at was at ISO 1250, and the second at ISO 3200, which strongly implies that you have Auto ISO turned on. And you were at f/36 at 1/4000 sec in the first frame, and f/36 at 1/500 in the second. That's more than a 4-stop difference in exposure once you take into account the different ISO as well as the change in aperture and shutter speed. That's why one image is almost black and the other is closer to a good exposure. The final stitched image contains photos with wildly different exposures, which is why it looks like it does.
The exposures are different because the camera was trying to compensate for the different light levels in each individual photo. A photo with a lot of sky looks very bright, so the camera chooses to darken the image, while the photo of the center of the cathedral looks darker, and the camera tries to increase the exposure to brighten it.
A couple of suggestions:
Put the camera on Manual mode, and set the ISO to a single value, NOT auto-ISO. Now, there are many combinations of ISO, aperture, and shutter speed that will give you the same "correct" exposure -- you just have to pick the best combination for the situation. Full daylight landscapes work well at ISO 100 or 200, apertures of around f/8, and whatever shutter speed gives the proper exposure. As the light levels drop, raise the ISO to compensate. On an overcast day like this, I'd probably shoot at ISO 400. For a stitched panoramic image, you'll want to make the exposure for the main subject, and keep that same exposure for all the other images in the pano. (For now, anyway.) Shooting in Manual ("M") mode makes this very easy, as the camera just shoots at whatever settings you have chosen, not thinking for itself. Shoot a photo of the cathedral, check it on the back of the camera, and if needed adjust your shutter speed, then take another test photo. Once you have your exposure worked out, shoot the individual photos that will make up the panoramic.
Oh, and avoid f/36, that's far too small an aperture for this camera. I wouldn't want to shoot smaller than f/11.
Good luck. If you reshoot this assignment, please post the results.