Lobster, bacon, lettuce, avocado, and tomato in a sandwich is not a bad thing. Quite the opposite, actually.
Kill the Bugs
Start by dispatching your lobsters with a knife to the brain stem. It's the fastest and most humane way to do it. (Your lobster will still twitch for a few minutes after death. These are reflexes, not conscious movements.)
Steam the lobster for exactly 2 minutes.
Roasting the lobster in the shell is gentle, which leads to even cooking and tender meat, as well as a concentration of flavor. I cook my lobster to 135°F, which takes about 7 minutes for claws in a 350°F oven, and 15 minutes for tails.
Chop and Season
After cooking, chill the lobsters in cold water. Then shuck, dry, and chop the meat. Season it with salt, pepper, chives, and a little bit of homemade mayonnaise. Just enough to bind it.
Score ripe tomatoes in an X shape on their bottoms with a sharp knife.
Immediately transfer them to cold water to halt cooking, then peel off their skins. It should rub off easily.
Quarter the Tomatoes
Quarter the tomatoes with a sharp knife to get at their innards.
Remove the seeds, jelly, and paler inner flesh from the tomato and save for another use (like sauce!).
Make the Mayonnaise
I make my mayonnaise in large batches so I'll always have some on hand. The easiest method I know is my Foolproof 2-Minute Mayonnaise. All you need is the ingredients, a hand blender, and a jar.
In moments, you've got creamy mayonnaise worlds better than what you can get in the store.
Shingle the bacon on a rimmed backing sheet, slightly overlapping each slice lengthwise and crosswise with its neighbors.
Cut the bacon sheet into perfect sandwich-sized slabs.
Spread Bread with Bacon Fat
Spread rendered bacon fat on the cut surfaces of a couple small loaves of ciabatta.
Toast the bread under the broiler until golden brown.
Shingle sliced avocado on the bread in a thin, even layer, pressing the avocado down into the soft part of the bread.
Add your bacon slab. It's ok if it breaks a little, just make sure you have 100% coverage.
Shingle on the tomato filets, pressing down firmly to compact all the ingredients.
Fill With Lobster
Fill the lettuce cup generously with the lobster salad and close up the sandwich.
Eat. With napkins.