6, ROUGHLY CHOPPED
1 SMALL, FINELY DICED
Fill the largest pot you have with at least 1 gallon of water and bring to a boil. Put the lobsters, two at a time, headfirst into the water. (Be sure to do it this way! If you put them in tail first, they will snap it back as they hit the water and could splash boiling water right into your face.) Cook, uncovered, for 5 minutes. This is just enough time to dispatch the lobster and firm up the meat inside the shell. With tongs, transfer the lobsters from the water to a colander to cool. Cook the two remaining lobsters in the same way.
Do not discard the cooking water.
Remove the lobster meat from the tail and cut into 1/2-inch dice. Remove the claw meat from the shell and reserve.
Combine the tomatoes, garlic, onion, olive oil, and 1 cup of the lobster cooking water in a medium saucepan. Season generously with salt and bring to a boil. Reduce the heat to a simmer and cook until the tomatoes begin to break down and the onion softens, about 5 minutes. Remove from the heat.
Add a good amount of salt to the lobster cooking water and cook the linguine, using the timing specified on the package. When the pasta is 1 minute from done, strain off all but 1/2 cup of the cooking water. Add the tomato sauce and continue to cook the pasta for another minute, until it has absorbed most of the liquid. Remove from the heat and toss in the chopped lobster tail meat and the cooked claws. Toss to combine.
Divide the linguine among 4 serving plates. Most of the lobster will fall to the bottom of the pan, making it easy to portion out. (Uneven distribution of the lobster can excite great envy and has the potential to cause fights, so try to get it right.) Place the claws on top of the pasta on each plate and sprinkle with the chives.