You’re looking for a few key signs. First, the meat should turn from that weird, translucent, “I-found-this-in-a-tide-pool” gray to a beautiful, solid opaque white. It’s like a magic trick you can eat.
Second, the meat should feel firm to the touch, but not like a rubber eraser. Give it a gentle poke. If it bounces back with a little sass, you’re winning. Third, and this is my favorite, the meat will start to pull away from the edges of the shell.
It’s like the lobster is saying, “I’m ready for my butter bath, please.” That’s your cue. Get that tail out of the oven immediately! Overcooked lobster is the saddest, toughest, most tragic thing in the culinary world. It’s the Jeans that don’t fit anymore—a real bummer.