Why does my macarons look like this

First time baking macarons and they turned out looking like this :( the taste is like a macaron but aesthetically they look....interesting. I think it might be because I undermixed the batter? or I didn't mix the meringue enough until stiff peaks formed. I put cream of tar tar in and let my egg whites age the day before to stabilize it, but I don't know which part of the baking turned out wrong.