Filling joint between backer board and wall in shower

I've never done home repairs before)

I just moved into a place and noticed GLOBS of silicone caulk in the walls next to the shower, it looked hideous. I went to shave some down and maybe recaulk a nicer bead, turned out the previous person used it to seal with tile backer with the wall.

Is this the proper way to do it?

My solution currently would be to patch it with joint compound to make it flush with the wall, and maybe caulk over the border with the tile. Is there a more proper way to do this? I'm concerned over keeping it waterproof. It appears the shower did have water leakage issues in the past.