Heat oven to 325 degrees. Grate the zest of the lemons into a small bowl. Squeeze the juice of the lemons into a separate bowl.
Season the brisket with salt and pepper. If the brisket is too big for the pot, cut it in two pieces (it will shrink as it cooks).
Over medium heat, warm a Dutch oven large enough to hold the brisket snugly and add the olive oil. When the oil is shimmering, sear meat until browned on both sides, about 5 minutes per side.
Add the lemon juice and cook for 5 more minutes, turning the meat over so it can absorb the juice.
Reduce the heat to low; add the broth, garlic and herbs, and bring liquid to a simmer. Cover the pot and place it in the oven. Cook until the meat is very tender, 2 ½ to 3 ½ hours, turning the meat three or four times while it cooks.
Uncover the pot and add the lemon zest, stirring it into the liquid. Continue to cook uncovered for another 15 minutes. Discard the herbs.
If you have time, let the brisket cool in the pot, then refrigerate overnight (see Tip). Otherwise, transfer brisket to a cutting board and slice the meat against the grain.
Skim the fat from the top of the sauce. (If you’ve refrigerated, it will have solidified, and you can pull it off.)
If the sauce seems thin when you remove the meat to slice it, put the pot on the stovetop and simmer it to thicken for 5 to 15 minutes. Taste sauce and add more salt and lemon juice as needed. Serve topped with any of the garnishes.
